Cool RF electrode

ABSTRACT

A system and method for applying energy, particularly radiofrequency (RF) electrical energy, to a living body can be used in tissue ablation and includes a combination of cannulas, guidance stylets, and a cooled high-frequency electrode.

TECHNICAL FIELD

This invention relates generally to the advances in medical systems andprocedures for prolonging and improving human life. The presentinvention relates generally to a system and method for applying energy,particularly radiofrequency (RF) electrical energy, to a living body.The present invention also relates generally to a system and method forapply energy for the purpose of tissue ablation.

BACKGROUND

The theory behind and practice of RF heat ablation has been known fordecades, and a wide range of suitable RF generators and electrodesexists. For example, equipment for causing heat lesions is availablefrom Radionics, Inc., located in Burlington, Mass. A research paper byE. R. Cosman, et al., entitled “Theoretical Aspects of Radio FrequencyLesions in the Dorsal Root Entry Zone,” Neurosurgery, Vol. 15, No. 6,pp. 945-0950 (1984), describes various techniques associated with radiofrequency lesions and is hereby incorporated by reference herein in itsentirety. Also, research papers by S. N. Goldberg, et al., entitled“Tissue Ablation with Radio Frequency: Effect of Probe Size, Gauge,Duration, and Temperature on Lesion Volume,” Acad. Radiol., Vol. 2, pp.399-404 (1995), and “Thermal Ablation Therapy for Focal Malignancy,”AJR, Vol. 174, pp. 323-331 (1999), described techniques andconsiderations relating to tissue ablation with radio frequency energyand are hereby incorporated by reference herein in its entirety.

Examples of high frequency generators and electrodes are given in thepapers of entitled “Theoretical Aspects of Radiofrequency Lesions andthe Dorsal Root Entry Zone,” by Cosman, E. R., et al., Neurosurg15:945-950, 1984; and “Methods of Making Nervous System Lesions,” byCosman, E. R. and Cosman, B. J. in Wilkins R. H., Rengachary S. S.(eds): Neurosurgery, New York, McGraw-Hill, Vol. III, pp. 2490-2498,1984, and are hereby incorporated by reference herein in their entirety.

The use of radiofrequency (RF) generators and electrodes in neuraltissue for the treatment of pain and functional disorders is well known.Included herein by reference, an as an example, the RFG-3C Plus RFGenerator of Radionics, Inc., Burlington, Mass., and its associatedelectrodes are used in the treatment of the nervous system, and thetreatment pain and functional disorders. The RFG-3C Plus generator hasone electrode output jack for connection to a single active electrode,and it has one reference electrode jack for connection to a referenceelectrode. When the active electrode is inserted into the body, and thereference electrode is placed, typically on the patient's skin, then RFcurrent form the RF generate flows through the patient's body betweenthe two electrodes. The generator can be activated and its signal outputcan be applied between the electrodes. Typically, this is referred to asa monopolar configuration because the active electrode is of smallerarea than the reference electrode, and so the concentration of RFcurrent is highest near it and the action of the RF electric field,whether for heating or for pulsed RF field therapy is greater there.This usually referred to as a single electrode configuration since thereis only one “active” electrode. Parameters that can be measured by theRFG-3C Plus RF generator include impedance, HF voltage, HF current, HFpower, and electrode tip temperature. Parameters that may be set by theuser include time of energy delivery, desired electrode temperature,stimulation frequencies and durations, and level of stimulation output.In general, electrode temperature is a parameter that may be controlledby the regulation of high frequency output power. Existing RF generatorshave interfaces that allow the selection of one or more of thesetreatment parameters, as well as various methods to display theparameters mentioned

The use of high frequency electrodes for heat ablation treatment offunctional disease and in the destruction of tumors is well known. Oneexample is the destruction of cancerous tumors of the kidney using radiofrequency (RF) heat ablation. A paper by D. W. Gervais, et al., entitled“Radio Frequency Ablation of Renal Cell Carcinoma: Early ClinicalExperience,” Radiology, Vol. 217, No. 2, pp. 665-672 (2000), describesusing a rigid tissue perforating and penetrating electrode that has asharpened tip to self-penetrate the skin and tissue of the patient. Thispaper is hereby incorporated by reference herein in its entirety.

Four patents have issued on PRF by Sluijter M. E., Rittman W. J., andCosman E. R. They are “Method and Apparatus for Altering Neural TissueFunction,” U.S. Pat. No. 5,983,141, issued Nov. 9, 1999; “Method andSystem for Neural Tissue Modification,” U.S. Pat. No. 6,161,048, issuedDec. 12, 2000; “Modulated High Frequency Tissue Modification,” U.S. Pat.No. 6,246,912 B1, issued Jun. 12, 2001; and “Method and Apparatus forAltering Neural Tissue Function,” U.S. Pat. No. 6,259,952 B1, issuedJul. 10, 2001. These four patents are hereby incorporated by referenceherein in their entirety.

United States patents by E. R. Cosman and W. J. Rittman, III, entitled“Cool-Tip Electrode Thermal Surgery System,” U.S. Pat. No. 6,506,189 B1,date of patent Jan. 14, 2003, and “Cluster Ablation Electrode System,”U.S. Pat. No. 6,530,922 B1, date of patent Mar. 11, 2003, and “Cool-TipRadiofrequency Thermosurgery Electrode System For Tumor Ablation”, U.S.Pat. No. 6,575,969 b 1, date of patent Jun. 10, 2003, describe systemsand methods related to tissue ablation with radiofrequency energy andelectrodes and are hereby incorporated by reference herein in theirentirety. One electrode system described in these patents comprises anelectrode with an insulated shaft except for a fixed uninsulated tipexposure of an uninsulated exposed length, the electrode beinginternally cooled so that the uninsulated exposed tip is cooled. Theelectrode shaft is a rigid and self tissue piercing with a sharp pointeddistal tip on the electrode shaft. This is essentially the configurationof cooled electrode offered by the Radionics Cool-Tip Electrode System(Radionics, Inc., Burlington Mass.) and the Valley Lab Cool-TipElectrode System (Valley lab, Inc., Boulder Colo.) that are describedlater in this section. This design of electrode has one disadvantagethat the initial insertion of the electrode can encounter tissueresistance which will displace the target volume, for example against afirm cancerous tumor, making it difficult to accurately position theelectrode tip at the desired target tissue. It has another disadvantagethat the clinician must inventory a multiplicity of electrodes havingdifferent lengths of tip exposure to accommodate his needs to createablation volumes of different sizes, for example, to accommodatedifferent sizes of tumors to be ablated. Another electrode systemdescribed in these patents comprises a system of a fully insulatedcannula, a pointed stylet that can be inserted into the cannula so thatthe sharpened tip of the stylet just emerges from the distal tip end ofthe cannula when the stylet hub engages the cannula hub, and a separatecooled uninsulated electrode that can be inserted into the cannula whenthe stylet has been removed. The electrode length is greater than thestylet length so that the distal end of the electrode extends beyond theend of the cannula distal tip by a predetermined length when the hub ofthe electrode engages with the hub of the cannula, and the amount thatit extends beyond the cannula tip is greater than the amount that thestylet extends beyond the cannula tip when the stylet is inserted intothe cannula. One disadvantage of this electrode system design is thatthe stylet does not protrude to an equal degree beyond the cannula tipas the electrode, so that the pointed stylet does not produce a tract inthe target tissue that can facilitate insertion of the electrode tip tothe desired target. Another disadvantage is that the sharp stylet doesnot extend significantly from the distal end of the cannula, so that thecool electrode when inserted into the cannula, after the stylet has beenremoved, must push through and penetrate the bodily tissue until thedistal tip of the cool electrode reaches a desire to target positionwithin the tissue, for example, at an appropriate point inside a tumorthat is to be ablated.

The Cosman G4 Radiofrequency generator (Cosman Medical, Inc.,Burlington, Mass.) is another example of a modern RF lesion generatorand the brochure printed in 2011 is hereby incorporated by referenceherein in its entirety.

The Radionics Cool-Tip Electrode System (Radionics, Inc., BurlingtonMass.) and the Valley Lab Cool-Tip Electrode System (Valley lab, Inc.,Boulder Colo.) are existing examples of cooled radiofrequency electrodesdesigned to ablate tissue in the living body, an example of which isablation of tumors. The brochures for these products are herebyincorporated by reference herein in its entirety. These electrodessystems comprise an electrode that has a partially insulated shaft, anuninsulated distal tip of known uninsulated length, and the distal tipis sharpened so that the electrode can pierce tissue and the bodilytissue to be positioned in a target position in the living body. Theuninsulated tip, and the electrodes connected to the output signal of ahigh frequency generator, will produce heating of the bodily tissue nearthe tip. The electrodes are also cooled by an internal fluid coolingsystem, and this has the effect of producing larger ablation volumeswhich can be desired, for example, to coagulate large tumors. Onedisadvantage of these electrodes is that they are supplied sterilepackaged and have a fixed uninsulated tip of a known length. This meansthat the manufacture and the hospital user must inventory a range ofthese electrodes with various lengths and tip exposures to accommodate atumor size related to a specific patient. Another disadvantage space isthat the sharpened distal end is in the shape of a trocar point, andthis produces a significant resistance force when inserting the tissuepiercing electrode into the bodily tissue. This can cause displacementof the tissue, especially full firm tissue and for firm tumor targetvolumes. A further disadvantage of these electrodes is that they havelarge hubs which are greater than 15 mm in diameter and are severalinches in length. These large hubs are necessary according to the designso that the clinician can have sufficient manual grip on the hub toimplement the forceful self piercing and penetration manipulation of theelectrode through the patient's skin and fur the wrong into the targetvolume within the bodily tissue, as for example, into a cancerous tumorthat is deep within the body. This disadvantage means that the electrodesystems are bulky and present a heavy and large hub structure. this canhave the disadvantaging of producing undesired torque and forces on theelectrode when inserted into the body causing potential inaccuracy andshift of positioning the electrode distal tip with respect to a desiredtarget position in the tissue. The large and bulky hubs have anotherdisadvantage that is more difficult to insert multiple independentelectrodes into the body in a tight cluster, because the large hubdiameter limits the closeness with which the electrodes and the hubs canbe clustered. In one case, this can be disadvantageous when multipleelectrodes are being passed between the space between the ribs toaccess, For example, a cancerous tumor in the liver or in the lung.

In a patent by Mark Leung, et al., entitled Electrosurgical TissueTreatment Method, U.S. Pat. No. 7,294,127 B2, date of patent: Nov. 13,2007; and, in another patent by Mark Leung, et al., entitledElectrosurgical Tissue Treatment Method, US patent number 2005/0177210A1, date of patent: Aug. 11, 2005, a cooled RF electrode is shown for anapplication in the field of pain therapy for bipolar lesion making inthe spine. These patents are hereby incorporated by reference herein inits entirety. The Baylis Medical Company offers a commercial version ofthe design shown in the patent these two patents, and the brochures forthese products are hereby incorporated by reference herein in itsentirety. These two patents and the Baylis product describes a system ofan insulated cannula with introducing stylet that emerges by a fewmillimeters from the distal end of the cannula, and substantially lessthan 10 mm. A high-frequency electrode can be inserted into the cannula,when the introducing stylet has been removed, and the electrode has adistal end which emerges from the end of the cannula when the hub of theelectrode in the cannula hub are engaged together. The distal end of theelectrode will emerge from the distal end of the cannula by a differentdistance than the distance that the distal end of the stylet from thecannula when the stylet is inserted into the cannula. In one electrodesystem of the Baylis products, the TransDiscal electrode, thehigh-frequency electrode also is adapted so that its distal portion thatemerges beyond the distal end of the cannula has a partially insulatedportion, and has an uninsulated exposed distal tip of the electrode thatis approximately 6 mm in length. In the Baylis products referred to byBaylis as Sinergy, Transdiscal, and Thoracool, the length of theuninsulated exposed conductive tip portion that is used to energize thetissue around the tip is between 4 and 6 mm. When the electrode isconnected to the output signal of a high-frequency generator, it is theuninsulated exposed distal tip of the electrode which is used to createthe thermal ablation. In all Baylis products, the high-frequencyelectrode shaft is completely insulated over the entirety or almost theentirety of the portion of the shaft that is inside the cannula, whenthe electrode hub is fully engaged with the cannula hub. Onedisadvantage of this design is that it either does not, or does notreliably, enable high frequency output signal to be conducted betweenthe electrode and the cannula. The cannula that is being used isinsulated over its entire length, including right up to the distal tipend, so that the cannula does not have any uninsulated portion toenergize tissue that surrounds the cannula when the cannula is insertedinto bodily tissue. As a consequence, when the electrode is connected tothe output signal of a high-frequency generator, the cannula itself doesnot deliver any output signal to the tissue in which it is placed. Thehigh-frequency electrode is also cooled by an internal fluid channel'sthat carry cooled fluid from a fluid supply external to the electrodethat can be connected to the electrode by tubes. The electrode of thesedesigns has a hub which has a diameter of greater than 13 mm. Onedisadvantage of TransDiscal Baylis electrode design is that the portionof the electrode that emerges from the cannula is not completelyuninsulated. Another disadvantage of this design is that the cannula iscompletely insulated preventing thermal ablation over the portion of thecannula shaft distal tip. Another disadvantage of this design is thatthe high-frequency electrode does not make reliable electrical contactwith the cannula when the electrode is connected to a high-frequencygenerator. The design of the fluid channel's in the electrode hub of thedevices shown the two referenced patents and in the Baylis brochurescomprise input and output fluid tubes into the hub structure in theinput and output fluid tubes are connected to fluid carrying tubes thatextend inside the electrode shaft and down to the distal end of theelectrode shaft. This design has the disadvantage that the input and theoutput tubes are incorporated within the hub structure, and the inflowand the outflow internal tubes within the electrode shaft occupying alateral displacement equal to the sum of the diameters of the internaltubes. These factors have the disadvantages that the hub diameter of theBaylis cooled RF electrode is 13 mm. This has the disadvantage that thediameter is sufficiently large that it restricts the use of multiplesuch Baylis electrodes in a cluster where the electrodes are insertedinto the tissue in a parallel array with the distance between the hubsless than 13 mm. Another disadvantage is that the cooling efficiency atthe tip of the high-frequency electrode is reduced by the fluidimpedance of the two internal tubes that extend inside and along theentire length of the electrode shaft. Another disadvantage is that theBaylis electrode designs is that they have an exposed electrode tiplength of only approximately 4 to 6 mm, and this is insufficient forablation of large target volumes such as large cancerous tumors whichcan be, in a in typical cases greater than 1 cm in dimension, and inother typical cases up to 4 cm, or 5 cm, or more in dimension. In all ofthe Baylis products, the electrode shaft comprises a plastic tube withdelicate flexible cooling tubes within. Only over approximately up to 6mm of the distal tip end if the shaft's outer material a conductivemetal. This has one disadvantage that the shaft is not robust to highlongitudinal or pushing force is as the electrode is passed into bodilytissue. Another disadvantage of the plastic shaft is that it is notrobust to lateral bending forces.

A wide variety of radiofrequency electric configurations are offered byCosman Medical, Inc. One example is the TIC Kit which comprises forequal length cannulas, each having different and known uninsulateddistal tip lengths. The Kit also comprises a stylet which can beinserted into each cannula to produce a sharpened occluded tip for thecombination of the cannula with the stylet when the stylet is insertedinto the cannula so that the hub of the cannula and the hub of thestylet are engaged with each other. The Kit also includes a fullyuninsulated high frequency electrode that can be inserted into each ofthe cannula, when the stylet has been removed, so that when theelectrode is connected to the output signal of a high-frequencygenerator, then the output signal will energize the uninsulated distaltip of the cannula. The electrode has an indwelling temperature sensorin its distal tip so that when the electrode is inserted into thecannula with the hub of the electrode is engaged with the hub of thecannula, the temperature sensor will measure the heating temperaturecorresponding to heating of the tissue around the uninsulated tip of thecannula. This electrode system was designed for coagulation of thetrigeminal nerve to treat trigeminal neuralgia. One disadvantage of thisdesign is that electrode system is not adapted to be cooled by aninternal cooling fluid, so this system is not suitable for ablation oflarge target volumes such as for cancerous tumors. Another disadvantageof this design is the uninsulated exposed distal tip lengths of thecannula are not greater than 10 mm, which is not adequate for mostablations of cancerous tumors.

The present invention overcomes the stated disadvantages and otherlimitations of the prior art.

SUMMARY OF THE INVENTION

In one exemplary embodiment, the present invention is directed towardssystems and methods for ablating tissue in the living body. This caninclude using a combination of insertion cannulas, rigid guidancestylets be inserted into the cannulas during initial placement in thebody tissue, and a cooled high-frequency electrode that can also beinserted into the cannulas after the stylet has been removed and thecannula is appropriately placed in the direction towards a decidedtarget volume in the bodily tissue. The cooled high-frequency electrodeis adapted for creating large ablation volumes. In one application, thepresent invention is directed towards thermal tissue ablation includingablation of cancerous tumors.

The present invention, in one example, is directed towards a system ofcannulas that can be directed percutaneously towards a target volumewithin the bodily tissue and guided by a rigid pointed tissue piercingstylet that can be inserted into the cannula, and a high-frequencyelectrode that can alternatively be inserted into the cannulas toproduce thermal ablation volumes in the tissue of the living body. Inone example the electrode can be a cooled electrode. In another examplethe electrode is a non-cooled the electrode.

In one embodiment, a high-frequency cooled electrode can have a slenderdiameter hub structure of about 10 mm or less to enable the use ofmultiple probes to be passed through multiple cannulas that are insertedtowards a target volume in a tight spatial cluster to create a largerablation volume, as for example, for the destruction of a largecancerous tumor. One advantage of this design is that it enables closeclustering of the cannula/electrode combination. Another advantage isthat by using a pointed stylet to be inserted into the cannula initiallyfor the placement of the cannula/stylet combination into the targetvolume, wherein, for example, the distal tip of the stylet relative tothe cannula is the same as the distal tip of the high-frequencyelectrode relative to the cannula, less force needs to be applied on thehub of the electrode to push it into the target volume because the rigidpointed stylet has produced a tract through the bodily tissue prior toinsertion of the electrode into the stylet. This has the advantage thatsmall diameter, shorter length, and more compact hub structures for theelectrode can be used because less manual force is required for initialinsertion of the electrode/cannula combination to achieve the targetvolume. The present invention describes several embodiments of suchcannula/guidance stylets/electrode configurations to achieve thisadvantageous objective which overcomes the disadvantages of electrodesystems in the prior art.

In one embodiment of the present invention, a system of cannulas ofdifferent lengths are used in combination with a sharpened guidancestylet or a needle type stylet, which for example can be a pointedneedle with its own internal stylet or a solid sharpened metal rod,which are adapted so that when the guidance stylet/needle is insertedinto each of the cannulas with the hub of the stylet engage with the hubof the cannula, then the distal tip of the stylet extends beyond thedistal tip of the cannula by a known and/or predetermined length, andthe combination of cannula with inserted stylet can be pushed easilyinto the bodily tissue so that the tip of the stylet can be positionedat a desired target location. In one embodiment, a high-frequencyelectrode, having substantially the same length as the stylet, can beinserted into the cannula, when the stylet has been removed, and theelectrode distal end extends beyond the cannula distal end by the sameknown and/or predetermined length as the stylet extends beyond thecannula distal end when it is inserted into the cannula. In one example,the portion of the electrode that extends beyond the cannula distal endis uninsulated. When inserting the electrode into the cannula after thecannula has been positioned and direct it into the body to use of thestylet/cannula combination, the electrode tip can reach a desired targettissue in the bodily tissue by following along the insertion tract madeby the guidance stylet. One advantage of this configuration is that itcomprises a single length of guidance stylet, and a single length ofhigh-frequency electrode, and, in one example, a multiplicity ofcannulas of different lengths so that different lengths of exposedelectrode tip can be achieved within the bodily tissue to accommodatepatient specific clinical needs and objectives. This has one advantagethat the appropriate cannula can be selected to accommodate the desiredablation volume according to the size of the target volume to beablated, for example, the size of a cancerous tumor to be ablated.Another advantage is that using one combined set of a multiplicity ofcannulas, a single guidance stylet, and a single high-frequencyelectrode, the clinician can select the appropriate a cannula for adesired length of electrode tip exposure beyond the end of the cannula.Another advantage is that the guidance stylets can have a conventionalbeveled needle point which is extremely sharp and facilitates tissuepiercing and penetration into even the toughest bodily tissues. Thismeans that the initial insertion of the cannula with a stylet in placecan be made very easily and with reduced pushing and manipulative forceby the clinician. Then subsequently, a high-frequency electrode can bepassed to the cannula, when the stylet is removed, for easy passage ofthe electrode to the target volume by the electrode following along thetract of the initial stylet insertion. This has one advantage that lessforce has to be inserted on a high-frequency electrode as it is beinginserted. This overcomes one disadvantage of the cooled electrodesystems of the prior art which have a fixed tip exposure for eachhigh-frequency electrode which means that a clinician must inventory andstock a multiplicity of these expensive electrodes to accommodatepatient specific geometries of target volumes that are to be ablated. Italso overcomes another disadvantage of the prior art cool electrodesystems, that the delicate high-frequency electrode does not have tohave a tissue piercing pointed tip. It also overcomes anotherdisadvantage of the prior art cooled electrode systems which have atrocar type pointed tip on the high-frequency electrode, which is lesswell adapted to easy tissue piercing and insertion into tough bodilytissues and therefore acquires more pushing and manipulation forces onthe prior art electrode systems for insertion into the body. Aconsequent disadvantage of the cooled electrodes of the prior art isthat they have hubs that are made larger than 15 mm in diameter and havea large physical size and weight to accommodate the increased pushingforce required to the insert them into the tissue of the body. Thismakes it disadvantageous to easily place and insert of clusters ofcooled electrodes of the prior art into a target volume, such as atumor, for the purpose of making a large ablation volume. Anotheradvantage of the present invention is that fluids, such as anestheticsand coagulants, can be injected through the introducer cannula eitherbefore or after the application of high-frequency output.

In one embodiment of the present invention, a system comprising acannula or cannulas, a tissue piercing guiding stylet, and ahigh-frequency electrode are adapted so that the length of the styletand the length of the electrode are substantially the same so that wheneach of the stylet or the electrode is inserted into any one of thecannula or cannulas, so that the hub of each of the stylet or the hub ofthe electrode engages with the hub of the cannula, the distal tip of thestylet and the distal tip of the electrode will be at the same positionrelative to the distal end of the cannula. One advantage of this designis that the combination of the cannula and sharpened stylet can beinserted into the bodily tissue so that the distal tip of the styletreaches a desired target position within the tissue, and then when thestylet is removed from the cannula, the electrode can be inserted intothe cannula, and the distal tip of the electrode will then be atessentially the same desired target position as was the distal tip ofthe stylet when it was inserted into the cannula. One advantage of thisdesign is that the sharpened stylet can act as a guide to produce atract into the tissue prior to the insertion of the electrode into thecannula, and therefore so that less force will be needed to be appliedto the electrode to the bodily tissue so that the electrodes distal tipis at a desired target position. This overcomes a disadvantage of thecooled electrodes of the prior art cited above wherein the cooledelectrode has a sharp point and must be pushed through a virgin paththrough the bodily tissue, which requires a substantial manual force tobe applied to the electrode during that pushing process.

In one embodiment of the present invention, a system comprising a set ofone cannula or multiple cannulas, a tissue piercing guiding stylet, anda high-frequency electrode are adapted so that the shaft of the cannulahas an insulated portion and an uninsulated cannula distal tip portionof known length, for a single cannula, or known different lengths, formultiple cannulas, and a tissue piercing stylet can be inserted into thecannula or cannulas so that the combination of the stylet and thecannula has a tissue piercing sharpened point, and the high-frequencyelectrode is uninsulated over at least a portion of its shaft length sothat makes electrical contact with the cannula or cannulas uninsulateddistal tips, and the electrode is adapted to be cooled internally sothat when inserted into said cannula or cannulas will cool theuninsulated distal cannula tip, and when said electrode is connected toa high-frequency generator, the output signal of the generator will beconnected through the electrode to the uninsulated cannula distal tip.One advantage of this system is that there is one guidance stylet andone high-frequency electrode in combination with either one cannula allwith multiple cannulas so that a known uninsulated portion of thecannula or multiple known uninsulated portions of the cannulas can beused to produce a desired known conductive tip length for tissueablation, which, in one example, can be approximately length of thedesired tissue ablation volume. One advantage is that the stylet withthe cannula can be used to produce the tissue piercing tract, andtherefore there can be less manual pushing force applied to theelectrode when it is inserted into the cannula so that the tip of theelectrode achieves essentially the same position relative to the distaltip of the cannula as the position of the stylet relative to the distaltip of the cannula when the stylet is inserted into the cannula. Anotheradvantage of the system is that a clinician can be offered multiplecannulas with different uninsulated distal tip lengths, together with asingle insertion stylet and a single high-frequency electrode, and theclinician can select the cannula distal tip length which is appropriatefor producing a desired ablation volume around the uninsulated cannulatip. This has the advantage of fewer parts to be inventoried by theclinician in the hospital. It also overcomes the disadvantage cooledelectrode systems of the prior art cited above wherein clinician orhospital has to inventory in sterile stock multiple high-frequencyelectrodes of different uninsulated tip lengths which is inefficient andexpensive since the high-frequency electrode itself is the mostexpensive part of the systems. Another advantage of one embodiment ofthis system is that the selected cannula couples to the electrode in apre-determined, rigid manner. Another advantage of one embodiment ofthis system is that the electrode and cannula can be coupled without theuse of a set screw or other adjustable device that involves anadditional manipulation in order to set the uninsulated tip exposurelength.

One objective of the present invention is to provide a system ofseparable cannula or cannulas, a guidance stylet that can be insertedinto the cannula or cannulas, and a high-frequency electrode that can beinserted into the cannula or cannulas to provide a separate tissuepiercing guidance system of the cannula or cannulas together with thesharpened stylet for initial access into the bodily tissue to bedirected towards a desired target volume or target position, and then tobe able to remove the stylet from the cannula or cannulas and insert thehigh-frequency electrode into the cannula or cannulas so that when thehub of the electrode and the hub of the cannula are engaged in a knownrelative position to each other, the distal tip of the electrode will bedirected towards the desired target volume or target position in thesame way as was the stylet when it was inserted into the cannula orcannulas. One advantage of the system is that the combination of cannulaor cannulas together with the stylet provides an entrance tract into thebodily tissue during the initial insertion process. Another advantage isthat less manual pushing force will be required to be applied to theelectrode when it is inserted into the cannula to achieve a desiredtarget position compared to a system of the prior art wherein theelectrode itself has a sharpened tissue piercing point which must bepushed into the bodily tissue.

A further embodiment of the present invention comprises a method andprocess of utilizing a set of one or more cannulas, an introducingstylet, and a high-frequency electrode to provide an access of thecannula with the stylet inserted in the cannula to be directed towards adesired target volume within the bodily tissue, and utilizing ahigh-frequency cooled electrode to be inserted into each of the one ormore cannulas so that the electrode distal tip is positioned issubstantially the same location relative to the distal tip of thecannula as is the distal tip of the stylet relative to the distal tip ofthe one or more cannulas when the stylet is inserted into the wild morecannulas.

The invention can be used in numerous organs in the body, including thebrain, spine, liver, lung, bone, kidney, abdominal structures, etc., andfor the treatment of cancerous tumors, other pathological targetvolumes, or other types of tissue target volumes in, for example,nervous tissue, bone tissue, cardiac tissue, muscle tissue, or othertypes of bodily tissues.

The details of one or more embodiments of the invention are set forth inthe accompanying drawings and description below. Other features, objectsand advantages of the invention will be apparent from the descriptionand drawings and from the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings that constitute a part of the specification, embodimentsexhibited various forms and features hereof are set forth, specifically:

FIG. 1A is a schematic diagram, in side elevation view, showing aninsertion, guidance, and electrode system comprising a partiallyinsulated cannula shown in sectional view, an introducing stylet with asharpened point shown in side elevation view, and a high-frequencyelectrode that can be internally cooled shown in side elevation view.

FIG. 1B is a schematic diagram, in side elevation view, of the sameelectrode system as in FIG. 1A showing the high-frequency electrodeinserted into the cannula with the hub of the electrode engaged with thehub of the cannula.

FIG. 2 is a schematic diagram in side elevation view showing a system ofa cannula that is partially insulated and has been exposed distal tip, astylet and/or needle that can be inserted into the cannula, and a cooleduninsulated high-frequency electrode that can also be inserted into thecannula wherein the stylet and the electrode have substantially the samelength.

FIG. 3 is a schematic diagram in side elevation view showing a system ofa cannula that has an insulated shaft, a stylet and/or needle with atissue piercing point that can be inserted into the cannula end extendsa distance out of the distal end of the cannula when the hubs of thecannula and stylet engage, and a cooled uninsulated high-frequencyelectrode that can also be inserted into the cannula end extends thesame distance out of the distal end of the cannula as does the styletwhen the hubs of the cannula and electrode engage.

FIG. 4 is a schematic diagram in side elevation view showing a system ofa multiplicity of cannulas that have shafts having a different shaftlengths, a stylet and/or needle with a tissue piercing point that can beinserted into any one of the cannulas, and the distal stylet extends adistance out of the distal end of any one of the cannulas by a knowndistance when the hubs of the cannula and stylet engage, and a cooleduninsulated high-frequency electrode that can also be inserted into anyone of the cannulas and electrodes distal portion distal portion extendsthe same distance out of the distal end of any one of the cannulas asdoes the stylet when the hubs of the cannula and electrode engage.

FIG. 5 is a schematic diagram showing placement of a high-frequencycooled electrode system into the tissue a patient's body so that theexposed tip extends into a target tissue, and a high frequency generatorwith graphic display of electrical parameters.

FIG. 6 is a flow chart of a process of inserting of an insulated and/orpartially insulated cannula together with a tissue piercing guidanceneedle and/or stylet system, followed by insertion of a high-frequencyelectrode into the cannula for the purpose of thermal ablation of thetarget volume.

FIG. 7 is a schematic diagram in sectional side elevation view showingthe internal fluid pathway and fluid channels through the hub in theshaft of a high-frequency electrode for compact and high efficiencyfluid coolant flow.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIG. 1A, an electrode system for tissue ablation inaccordance with the present invention is shown in schematicrepresentation, comprising at least one cannula, a guidance styletand/or needle that can be inserted into the cannula, and ahigh-frequency electrode that can also be inserted into the cannula,when the guidance stylet is removed. The cannula as shown in sectionalside elevation view and has a shaft 101 of length D. In one example, thecannula shaft 101 has a proximal portion 107, represented by the hatchedarea, of length E that is insulated and the distal portion 111 of lengthU that is uninsulated. On the proximal end, the cannula shaft isconnected to a hub 120. The hub can have engagement surface or shoulderrepresented by 122, which, for example, in one embodiment can be a luertaper. The cannula has an opening 112 through it, the opening 112connecting to an opening in the distal tip 114. In one example, thedistal tip 114 can be a squared off end. In another example the distaltip opening 114 can have a beveled or tapered configuration. In oneexample, the cannula can be comprised of a metal tube 104 that is partof the cannula shaft 101. In one example, the metal tubing 104 can be,for example, a stainless steel tubing or other metal material that thisconductive. In one example, the uninsulated distal portion of the shaftcan have a length U that is nonzero. In another example, the uninsulatedportion of the cannula shaft can have a length U that is essentiallyzero in length, and therefore, in that example, the insulated portion107 has a length E that is substantially equal to the external length Dof the shaft. In one example the uninsulated length U and the overallshaft length D can be known and predetermined, and suited and adaptedfor insertion into the bodily tissue to a certain length to accommodateclinical needs, such as for example approaching a cancerous tumor volumeat a certain depth beneath the skin. In another example, the system ofFIG. 1 can include multiple cannulas each of which have differentuninsulated tip lengths U to accommodate clinical needs. For example, ifthe uninsulated portion 111 is used to energize tissue near it with highfrequency output signal, when the cannula is inserted into bodilytissue, a selection of cannulas with differing tip lengths U can beuseful to match the volume of ablation that is desired. Another example,the embodiment can comprise multiple cannula each with different shaftlengths D to accommodate different total uninsulated tip exposure whenthe high frequency electrode is inserted into the cannula, and/ordifferent depths of penetration of the cannula shaft when it is insertedinto bodily tissue.

Referring FIG. 1A, a stylet structure 127 is shown in side elevationview and is adapted to be inserted into the lumen 112 of the cannula101. The stylet structure has a shaft 128 which has a nominal length L.The shaft 128 can pass through the lumen opening 112 in the cannula. Inone example, the stylet shaft 128 is uninsulated and is made ofconductive material, such as, in one example, a solid metal shaft. Inanother example the shaft 128 can comprise a needle structure thatincludes a hollow sharp and pointed needle with its own obdurating innerstylet. In one example, it has a distal tip 129 which has a sharpenedtissue piercing point. In one example, it has a hub structure 132 whichcomprises a Luer taper surface 137 that is adapted to engage, in oneexample, with the luer engagement surface 122 of the at least onecannula 101. In one example, the stylet structure 127 is adapted so thatwhen it is inserted into the cannula 101, and the hub 132 of the styletstructure engages with the hub 120 of the cannula, then the uninsulatedexposed conductive surface of the shaft 128 extends beyond the distaltip 114 of the cannula by the distance T. The length L of the styletstructure and the length D of the cannula can be predetermined and/orselectable so that the degree of tip extension length T of the styletstructure beyond the distal end of the cannula 114 is a known, and/orpredetermined/and/or selectable length to accommodate the clinical needsfor a given patient and a given target structure objective.

Referring to FIG. 1A, a high-frequency electrodes 140 is shown insideelevation view. The electrode comprises an electrode shaft 144 which hasa proximal end and has a distal end which terminates in a distal tip149. In one example, the electrode shaft 144 is completely uninsulated.In one example, it can comprise a metal tubing, such as, for example, astainless steel tubing. In another example, the electrode shaft cancomprise a conductive material. In another example, the electrode shaftcan be partially insulated. In another example, the electrode shaft caninclude plastic and other non-conductive materials. The electrode can beadapted to be inserted into the through-opening 112 of the cannula 101,when the stylet 127 is removed from the cannula 101. In one example, thehub can comprise a luer tapered 147 which is adapted to engage, in oneexample, a luer engagement surface 122 of the cannula hub 120. Theelectrode has a connection 158 which can be a cable or wire connectionthat is adapted to be connected to a high frequency generator so thatthe output signal of the high frequency generator can be connected tothe uninsulated portion of the electrode shaft 144. Therefore, when theelectrode 140 is inserted into the cannula 101, and when the cannulashaft comprises a metal tubing 104, and when the output signal from thegenerator is connected to the shaft 144, in one example, than theexposed conductive electrode shaft 144 can make electrical contact withthe cannula metal tubing shaft 104 so that the output signal can beconnected thereby to the exposed an insulated cannula distal tip 111. inone example, electrode 140 can have a non-cooled electrode shaft 144. Inone example, electrode 140 can have an internal cooling channel so thatthe shaft of the electrode 144 can be cooled by a cooling fluid runninginside the internal cooling channel. In one example not shown explicitlyin FIG. 1A, electrode 140 can have an internal cooling channel and anaperture at its distal end so that some or all of the cooled fluid, suchas sterile saline or sterile water, enters the tissue in which theelectrode is placed. A cooling fluid can flow into the electrode by aninput tube 151, and the cooling fluid can flow out of the electrode byan output to 154, the arrows 162 and 164 representing schematically thedirection of input and output flow of the cooling fluid into thosetubes, respectively. The cooling fluid can be supplied by an externalcoolant supply, not shown in this figure, which is similar to that usedin the cool the RF electrodes systems of the prior art referred to inthe BACKGROUND section above. In one example electrode, 140 can have aninternal temperature sensor within the shaft 144 at a selected positionin the shaft which, for example in one embodiment can be near the distaltip 149. In one example, the distal tip 149 can be a non-tissue piercingshape, for example, a bullet shaped, or a hemispherical shape, or ablunt conical pointed shape, or other shape that does not have a sharptissue piercing profile. In another example, the electoral distal tip149 can have a tissue piercing sharpened shape such as a trocar shape,or in another example a needle bevel type shape such as a sharpenedtri-cut needlepoint.

Referring to FIG. 1A, in one example, the stylet shaft length L of thestylet structure and the length of the electric shaft 144 shown in FIG.1A is also L. In this example, the shaft lengths of the two structures,the stylet structure and the electrode structure are substantially equalas shown in FIG. 1A. The length L can, for example, be measured in thecase of the stylet from the distal edge 139 of the hub luer surface 137to the very distal end of the pointed tip 129. Some variation of thislength L can, for example, involve measuring to the midpoint of thebevel edge 129. The length L as measured on the electrode 140 can, inone example, be from the distal end 142 of the luer engagement surface137 to the very distal tip and 149.

Referring to FIG. 1B, a side elevation view is shown of the combinationof the electrode 140 inserted into the cannula 101 so that the electrodehub 145 engages with the cannula hub 120. The insulated portion of thecannula shaft is 109 as indicated by the hatched area. The exposeduninsulated tip in this example comprises the combined uninsulatedlength of the cannula distal expos tip 111 which has length U togetherwith the portion of the electrode shaft 144 that extends beyond thecannula distal opening 114, that extension portion of the electrodebeing designated as 164 in FIG. 1B and being specified as having lengthT in FIG. 1B. Therefore, the combined uninsulated exposed tip in thisexample is a combination of portion 111 of the cannula and the portion164 of the electrode, meaning that the length of the total exposed tipis the sum of U plus T. when the electrode shaft 144 is connected to theoutput signal of a high frequency generator by the wired connection 158,then the electrical connection of the electrode to the metal cannulatubing means that the entire exposed tip, 111 and 164, are connected tothe output signal of the high frequency generator. In one example, ifthe output signal of the high frequency generator is specified asvoltage V, and that voltage will be connected to the combined expose tip111 plus 164 having length U plus T. In one example, if electrode 140 iscooled by in total fluid as described above, then the entire combinedexposed conductive tip will be cooled because of the thermal contactbetween the electrode shaft 144 and the cannula shaft 104.

Referring to FIG. 1A and FIG. 1B, because the shaft length of the styletstructure and the shaft length of the electrode are both substantiallyequal to the length L, then the degree of extension T of the styletdistal end from the distal end 114 of the cannula when the stylet isinserted into the cannula so that the stylet hub in and engaged with thecannula hub is substantially the same as the degree of extension T ofthe electrode shaft beyond the distal end of the cannula. Therefore,when the stylet 127 is inserted into the cannula 101, than the combinedsystem can be manually percutaneously pierced and penetrated through theskin of the patient's body and into the depth of the bodily tissue. Thetissue piercing tip 129 of the stylet 127 will produce a guide tract ofthe combined structure direct the towards a target volume so that thetip 129 can be positioned to end at a desired target position in thebodily tissue. Then, when the stylet 127 is removed from the cannula101, and the electrode 140 is inserted into the cannula 101, theextended portion 164 of the shaft of the electrode 140 will pass alongthe tract established by the stylet, and because the electrode and thestylet have the same shaft length, then the electrode distal tip 149will then be at the same target position as was achieved by the styletdistal tip 129. Functionally, the stylet which is a rigid tissuepiercing structure therefore establishes a pathway through the bodilytissue, so that subsequently the insertion of the electrode through thecannula when the style has been removed, will be far easier to carry outand require far less mechanical pushing and manipulating forces on theelectrode. This has the advantage that the sharpened rigid stylet can beutilized in an efficient and ergonomic manner to achieve positioning ofthe cannula in a desired direction within the tissue to form a tract toa target position, and therefore a simplified way of passing theelectrode within the cannula to place the tip of the electrode at adesire to target volume and target position within the bodily tissue.Accordingly, the combined exposed conduct the tip 111 plus 164 can bepositioned in a correct direction and position with respect to a targetvolume, such as a cancerous tumor, so that when the combine tip 111 plus164 is electrified by the output signal of a high frequency generator,then they thermal tissue ablation can be achieved in the tissue near thecombined tip. The embodiment of FIG. 1A and FIG. 1B can comprise morethan one cannula represented by 101, and each of the different cannulascan have different lengths different lengths D, and different tipexposed lengths U, so that different degrees of combined tip exposures111 plus 164 can be achieved to accommodate clinical needs, as forexample, the size of the target volume to be ablated, and also toaccommodate a desired depth of penetration of the cannula shaft into thebodily tissue beyond the level of the patient's skin to reach theappropriate internal target volume, such as for example a canceroustumor within the depths of the bodily tissue.

Referring to FIG. 2, an example of an embodiment of the presentinvention is shown in schematic and side elevation views. A cannula 201has a shaft with an insulated portion 204, indicated by the hatchedarea, having length E, and with an un-insulated distal portion 207 oflength U. The cannula has a distal tip 211 which has a sharpened pointconfiguration. The cannula has a hub to 220 which has a female luertapered internal diameter which can act as an engagement surface whenthe stylet or the electrode is inserted into the cannula. The stylet127, in one example, comprises a rigid metal shaft 128 which has alength L and the rigid shaft can be an uninsulated metal shaft. Inanother example, the cannula shaft 128 can be a plastic shaft with asharpened tip. The stylet has a hub 232 that has a male luer taperedsurface 237 for engagement with the cannula's female Luer hub surface222 when the stylet is inserted into the cannula. The stylet distal tip239 has a sharpened beveled shape so that when the stylet is insertedinto the cannula 201, the beveled tip of the stylet matches the beveledsharpened shape 211 of the cannula. Therefore, in the initial insertionprocess into the bodily tissue, the stylet that can be inserted into thecannula so that the hub of the stylet let and the hub of the cannula areengaged together, and their combined distal tip has the configuration ofa sharp tissue piercing end which is adapted for piercing andpenetrating the patient's skin and the patient's bodily tissue as thecombined structure is manipulated by the clinician in the appropriatedirection and with the appropriate depth so that the distal exposed tip211 can be positioned within a desired target volume, such as a volumethat is to be thermally ablated when the electrode is connected to theoutput signal of a generator. In one example, the distal end 239 of thestylet 127 does not extend substantially beyond the distal end 211 ofthe cannula 201, when the stylet 127 is engaged in the cannula 201. Inone example, the distal end 239 of the stylet 127 extends only slightlybeyond the distal end 211 of the cannula 201, when the stylet 127 isengaged in the cannula 201. In one example, the cannula 201 can have aclosed distal end 211. In other examples, different types of engagementsurfaces can be designed in the hub of the cannula, the hub of theelectrode, and or stylet that are different from the Luer taper. Thesecan involve mating surfaces, locking or twist locking devices, and othercommon hubs found on needles and cannula in the medical industry. In oneexample the stylet 127 can be a solid stainless steel rigid metal shaftwith a sharpened point 239. In another example the system of styletsystem 127 can comprise a hollow stainless steel needle with, forexample, an obturating stylet within it that closes the end 239 to makea flush sharpened tissue piercing tip. Another component of theelectrode system in FIG. 2 is a high-frequency electrode 240 whichcomprises an electrode shaft 242, which has on its proximal end a hub248 with a Luer engagement surface 251 that can engage with the Luer hub222 of the cannula when the electrode is inserted into the cannula. Thelength of the electrode shaft 242 is designated as L, and this can be,in one example, essentially the same length L as the stylet system shaft128. In one example, the distal end 244 of the electrode 240 does notextend substantially beyond the distal end 211 of the cannula 201, whenthe electrode 240 is engaged in the cannula 201. In one example, thedistal end 244 of the electrode 240 extends only slightly beyond thedistal end 211 of the cannula 201, when the electrode 240 is engaged inthe cannula 201 In one example the electrode distal tip shape 244 can bea sharpened point that is adapted for tissue piercing. In anotherexample the electrode distal tip shape 244 can be more of a conical orbullet shaped point which makes it adaptable to follow a tissue tract inthe bodily tissue. In another example, the tip 244 can be ahemispherical smooth tip which is not tissue piercing. In one example,the electrode 240 has an electrical connection wire 260 that canconnected to the output signal of a high-frequency generator, not shownin this FIG. 2. When the connection 260 is made to a generator, theoutput signal of the generator can be connected to the shaft 242. In oneexample the shaft 242 is uninsulated and electrically conductive over atleast a portion of its shaft so that when inserted into the cannula 201,electrical contact is made between the electrodes 240 and the conductiveexposed tip 207 of the cannula. Therefore when the cannula and theelectrode are combined, the output signal of the generator can beconnected to the exposed tip 207, so that when the combined cannula andelectrode within the bodily tissue, tissue near the exposed tip 207 canbe heated by the output signal to cause a thermal ablation zone aroundthe tip 207. In one embodiment the electrode 240 is a non-cooledelectrode. In another example, the electrode 240 can have an internalcooling channel through which a coolant fluid from an external coolingsupply, not shown in FIG. 2, can flow through the internal channel incool electrode 240. When the electrode 240 is inserted into the cannula201, the exposed tip 207 of the cannula can also be cooled by thermalconduction between the cannula 201 and the electrode shaft 242. Theexample of FIG. 2 can also comprise a multiplicity of cannulas, eachhaving different exposed tip lengths U of the exposed tip 207. In oneexample, the system can comprise a set of cannulas each having differentvalues of exposed length U that can be predetermined and known so thatthe clinician can select the cannula with the appropriate exposed tiplength that is desirable to ablate a tissue volume of known size. In oneexample, the multiplicity of cannulas can be used with a single styletsuch as 127 and with a single high-frequency electrode such as 240. Oneadvantage of the system presented in FIG. 2 is that a set of cannulaewith differing tip exposures U can be created for a given electrode andstylet, both of length L, by putting varying lengths of insulation E onmultiple cannula shafts of with the same length E+U. Another advantageof the system presented in FIG. 2 is that a rigid cannula 201, onceinserted into bodily tissue, creates a fixed channel within the tissueinto which the stylet 127 and electrode 240 can be interchanged. Anotheradvantage of the system presented in FIG. 2 is that, if the stylet 127and electrode 240 do not extend substantially beyond the end of thecannula when they are each engaged in the cannula, interchange of thestylet 127 and electrode 240 within the cannula 201 placed in bodilytissue does not substantially change the extent of the assembly thatcontacts the tissue.

Referring to FIG. 3, another embodiment of the present invention isshown in side elevation view of its assembled components. In the upperof portion of the FIG. 3, embodiments of the system similar to that ofFIG. 1A is shown in which the cannula 301 is completely insulated withinsulation 304, indicated by the hatched area, and therefore the lengthof the cannula D is equal to the length of the insulated portion E asdesignated in FIG. 1A. A stylet system 307 is inserted into the cannula301 so that the electrode hub 322 is engaged with the cannula hub 320 bymeans of a Luer taper surface 327. When that engagement of hubs is made,the distal portion 312 of the stylet 307 extends beyond the distal end312 of the cannula 301 by a distance T. The distal stylet portion 307that extends beyond the cannula distal end 314 can be a rigid tissuepiercing structure with a sharpened tissue piercing and penetratingdistal tip 310. In one example, the stylet structure can be a rigidmetal tubular structure such as a sharpened needle. In another example,the stylet can be a solid structure such as a solid metal steel rod witha pointed tip or it can be a rigid firm plastic rod with a pointed tip.In one example, the distal tip 310 can be a needle like level, forexample, a beveled shape point, or a tri-cut beveled tip. In anotherexample, the tip 310 can be a trocar point or other pointed structuresuch as a sharpened conical structure. In one example, the designationof the overall length of the stylet structure as shown in FIG. 3 can bespecified as LL. In the lower portion of FIG. 3, the same cannula 301 isshown with a high-frequency electrode 342 inserted into it, so that theelectrode hub 348 engages with the cannula hub 320 by means of a Luertaper 351. In one example, the distal portion 347 of the electrode shaft342 extends beyond the distal tip 314 of the cannula 301 by the distanceT. This electrode extension distance can be, in one example, essentiallythe same as the stylet system extension distance shown in the upper FIG.3 in the situation where the stylet is inserted into the cannula. In oneexample, the electrode extension portion 347 can be uninsulated so thatwhen the electrode is connected to a high-frequency generator byconnection wire 360, the output signal of the generator can be connectedto and energize the exposed distal surface 347. In that case, when thecombination of the cannula and the electrode is inserted into the bodilytissue, the output signal from the generator that is connected throughthe distal tip 347 to the surrounding bodily tissue can cause theheating and ablation of the tissue around the exposed distal electrodeend 347. In one example, the shape of the electrode distal tip 344 canbe a smooth rounded shape not adapted for tissue piercing, but adaptedto follow a tract in the tissue made before hand by the tissue piercingstylet structure 312 and 310 shown in the upper figure in FIG. 3. Inanother example, the electrode distal tip can have a bullet shaped orconical shaped configuration which can enable the electrode 347, wheninserted into the cannula 301, after the stylet 307 has made a tissuepenetrating tract in the tissue, to follow the tract made by the tissuepiercing extension 312 of the stylet 307. As shown in FIG. 3, in oneexample, the length of the extension of the electrode 347 beyond thecannula distal end 314 can be specified as T, and this distance can beessentially the same as the distance of extension of the sharpenedstylet distal end 312 beyond the cannula distal tip 314. In one example,the electrode length as shown in FIG. 3 from the electrode hub referencepoint to the distal tip of the hub can be specified as LL which isessentially equal to the length specified for the equivalent points ofthe stylet system in the upper figure of FIG. 3. In one example, thelength of the electrode shaft 342 and the length of the hubs shaft 307can be made so that the very distal portion of the electrode tip 344extends beyond the cannula distal end 314 by the same amount as the verydistal end of the point of the cannula 310. In another example, thelength of the stylet shaft and the length of the electrode shaft can beadapted so that the very distal end 344 extends beyond the cannuladistal end 314 by the distance that the base of the sharpened tip 311extends beyond the cannula distal end 314. Typically, a sharpened pointsuch as 310 of the stylet system is not very long compared to the lengthof the exposed extension tip, so that some small variability in thematching of the lengths LL for both the stylet shaft and the electrodeshaft can take into account the definition of the tip and geometry 310of the stylet and the tip and geometry 344 of the electrode. In oneexample, the essential equivalence of the lengths of these two shaftstakes into account small variations of definition of the distal end ofthe cannula shaft point and the distal end of the electrode shaft. Inone example, the cannula 301 can have distance markings along its shaftas indicated by the lines 317, 318, and 319 as shown in FIG. 3. In oneexample, these lines can be centimeter markings so that each centimetermarking corresponds to a distance between the distal face 325 of the hub320 and the cannula distal tip 310 of the stylet structure when insertedinto the cannula, or between the cannula hub distal face 325 and thedistal end of the electrode 344 when the electrode is inserted into thecannula. In another example, each line can correspond to the distancefrom the distal end of the electrode and/or stylet to the markerposition when the electrode and/or stylet is respectively engaged in thecannula. These markings can, for example, correspond to a measure of thedistance along the length corresponding to D plus T. This can help theclinician determine, in this situation, when the combination of thecannula plus the stylet or the combination of the cannula plus electrodehas been inserted into bodily tissue. By observing which markercoincides with the patient's skin, the clinician can then infer orcalculate the remaining distance along the total shaft distance D plusT. corresponding to the tip of the extension of stylet or the cannula.This can help clinician gauge and calculate the total depth ofpenetration from the skin surface to the distal end of the electrode,and this can assist in confirming that the distal end of the electrodeis properly placed in a desired target position, such as in a canceroustumor, deep within the body. If a desired target position for example isknown to be at a certain depth of penetration beyond the patient's skinand in a given direction, the presence of these distance markings on thecannula shaft can confirm that the electrode tip is at the proper depthof penetration. Such distance markings, can in one example, thepermanent ink markings on the insulation 304. In another example thedistance markings can be black etched lines on the stainless steeltubing that makes up the shaft of cannula 301, and the insulation 304can be sufficiently transparent that the markings can be visible throughthe insulation. In one example, the markings on the cannula can be inmillimeters, or in centimeters, or in some fractional amount betweenthese increments. Although such distance markings are not shownexplicitly in the embodiments shown in FIGS. 1, 2, 4, 5, and 7, it isintended that these embodiments can also comprise such distancemarkings. In one example, an embodiment of the present invention cancomprise a set of multiple cannulas, a stylet, and an electrode, andthese can be can be constructed so that the distance D plus Tcorresponds to a known length such as, for example, 10 cm, 15 cm, 20 cm,25 cm, 30 cm, 35 cm, 40 cm, 50 cm, 60 cm, 70 cm, 80 cm, 90 cm, 100 cm,or longer, or some other selected or known predetermined total shaftlength corresponding to the distance from the cannula hub to the distaltip of the electrode beyond the cannula. The set of the multiplecannulas, single stylet, and single electrode having a specified valueof D plus T, and each particular cannula has a specified length D toprovide a specific tip extension length T. In one example, thesespecific extension lengths T for the different cannulas can be specificconvenient lengths such as 1 cm, 2 cm, 2.5 cm, 3 cm, or 4 cm. In anotherexample these extension length T. can be in the range of 5 to 10 cm, orlonger. The clinician can then select one of the multiple cannulas sothat the electrode extension length T can correspond closely to thedesired length of ablation volume, which, for example, can be determinedby the size of a cancerous tumor to be ablated. This has one advantagethat the exposed tip lengths of the extension beyond the cannula tip issufficient to ablate large tumors which can in many examples be greaterthan 1 cm in length, and other typical cases as great as 4 cm in lengthor in another clinical examples as large as 5, 6, 7, 8, 9, 10,centimeters or even greater in length. In one example, the cannula 301can have a shaft which is made of a thin plastic tubing material havingmarkings along its external surface corresponding to a determinedmillimeters or centimeter distances. In another example, the cannula canbe a metal tubing which has etched millimeter and or centimeter distancemarkings On it, and the metal tubing can be insulated by a transparentor translucent dielectric insulating material such as a heat shrinkTeflon tubing or some other heat shrink polymeric plastic tubing so thatthe millimeter and/or centimeter markings can be seen and visualizedthrough the insulation coating.

Referring to FIG. 3, in one example, the cannula shaft 301, the styletshaft 307, and the electrode shaft 347 can comprise etched, sandblasted,grooved, or otherwise interrupted surface markings that are visible onultrasonic imaging that is carried out during the operators procedurewhen the cannula plus stylet and the cannula plus electrode has beeninserted into the patient's body. In one example, the distal portion ofthe cannula shaft 301 can have a band of etched or interrupted surfacemarkings around its circumference that can be visible under ultrasonicimaging. In one example, the last approximately 0.5 cm, or 1 cm, orother length portion of the distal end of the cannula shaft 301 can havean interrupted echogenic surface on its metal tubing. A thin plasticinsulated coating above this interrupted surface will not degrade itsvisibility in ultrasonic imaging. Such an interrupted surface that isvisible in ultrasound can be referred to as an echogenic or ultrasoundvisible marking. Variations of the pattern, position, or length of theultrasonic visible markings can be made on the cannula, such as, forexample, separated bands of ultrasonic visible markings spaced apart bya known distance. In another aspect, the stylet 307 can have on itsdistal portion echogenic markings such as bands of interrupted surfaceson its metal surface that are visible to ultrasound. In this way, whenthe combination of cannula with a stylet inserted is penetrated into thepatient's tissue towards a target position, the clinician can apply inultrasonic imaging device to the patient's skin and visualize real-timethe echogenic markings on the cannula and/or the stylet which willprovide the clinician with real-time visible imaging data related to theposition of the tip of the stylet and/or the position of the distal endof the cannula relative to anatomical objects of interest. This providesthe clinician way of confirming that the position of the cannula/styletsystem has been placed in a desired position relative to a target volumesuch as a cancerous tumor volume, and also provides the clinician withthe way of confirming that the ablation electrode is not too close tocritical mobile structures nearby. Many biological target volumes, forexample certain cancerous tumor volumes, are also visible on ultrasonicimaging. Therefore, an advantage of having echogenic markings on thecomponents of the present invention is that it enhances the clinician'sability to confirm and to make real-time course corrections during thesurgery to position the elements of the present invention at desiredlocations in the patient's body. In another aspect, the distal portionof the electrode 347 can have echogenic markings on its metal surfacethat are also visible to ultrasound imaging. In one example, a band oflength approximately 5 mm, or 10 mm, or 15 mm, or some other length, ofinterrupted echogenic surface on the metal surface of tubing 342 canprovide an echogenic surface detectable by intraoperative ultrasoundimaging. In one advantage, having both the cannula and the electrode andthe stylet having echogenic markings is that it will give the clinicianan indication of the overall length of the tip extension of theelectrode 347 beyond the cannula tip. The clinician then has a guide asto where the position of the heat ablation tip is located relative tohis desired target volume. In another example, the cannula 301 does nothave echogenic markings, and the electrode 342 can have an echogenicsurface markings over its entire extended length beyond the tip of thecannula. In this example, as illustrated in FIG. 3, the electrodeextending surface portion 347 is the conductive surface that willproduce the ablation heating when it is electrified by the output signalof the generator. Therefore, being able to visualize that ablation tipreal-time during the surgery provides the advantage that the clinicianhas knowledge before hand of where the ablation will take place relativeto his selected targets. Another advantage of echogenic markings on thecomponents of the present invention that are illustrated in theembodiments of FIGS. 1 through 7, is that the clinician can visualizethe position of these components relative to normal anatomical objectsas well as pathological objects near the path of the electrode system.In one example, the surgeon can desire to avoid a critical normalanatomical structure such as the intestine of the bowel, and having theultrasonic real-time information on the position of the electroderelative to these delicate structures can be critical to avoid unwantedablation of normal tissue. Another advantage is that it can allow theclinician more certainty in placing the electrode in the correctdirection in the depth of the patient's tissue to adequately cover thetarget volume to be ablated. Another advantage is that when multipleelectrodes are used in the same patient, for example for enlarging theablation volume, the relative position of the multiple electrodes can bevisualized real-time during the surgery and allow the clinician to makeappropriate adjustments so that the spacing between the multipleablating tips is appropriate to optimize the size of the ultimateablation volume. Another advantage, is that by having the ultrasonicimaging information, as well as the imaging of surrounding anatomy andpathology using ultrasound, the surgeon can optimize the placement ofone or more ablation electrode system relative to the anatomy accordingto a preplanned of this electrode positions which the clinician can havemade based on pre-surgical imaging data for example from CT, MRI,ultrasonic imaging studies of the patient. This then would show up onultrasonic imaging to give the clinician a location of the position ofthe ablative tip of the electrode in real-time during interruptedsurgery. The use of ultrasonic imaging during interventional surgery iscommonplace in modern operating theaters or procedure rooms. Thereexists already the practice of making echogenic markings on needles andcannula that are used for biopsy or other interventions. Ultrasoundimaging is also used commonly to visualize pathologies such as tumors inthe living body during surgery during diagnostics. The use of echogenicmarkings can similarly apply to the other embodiments of the presentinvention as illustrated and described herein related to the FIGS. 1through 7. One advantage of using echogenic markings on the componentsof the present invention, including cannulas, stylet, and electrodes, isthat it can give the clinician in real-time graphic imagingrepresentation of the position of the conductive tip portions of theentire electrode system relative to the target volume which is to beablated. Another advantage is that it allows the clinician to makereal-time adjustments of the positions of the cannula, stylet, and/orelectrode during the procedure relative to known anatomy, bothpathological as well as normal anatomy, so as to navigate the direction,the depth, in the appropriate conductive tip exposures of these elementsto optimally treat the desired target volume.

In one example, the cannula 301 can each have a variation in density atits distal end 314 so that its distal end 314 can be distinguished inx-ray, CT, or other radiographic images. In one example, the introducerstylet 307 can each have a variation in density at its distal end 310 sothat its distal end 310 can be distinguished in x-ray, CT, or otherradiographic images. In one example, the electrode 342 can each have avariation in density at its distal end 344 so that its distal end 344can be distinguished in x-ray, CT, or other radiographic images. In oneexample, the cannula 301, the introducer stylet 307, and the electrode342 can each have a variation in density at their respective distal ends314, 310, and 344 so that each of these distal ends 314, 310, and 344can be individually distinguished in x-ray, CT, or other radiographicimages. One advantage of this design is that the extent of the tiplength T can be visually identified in x-ray, CT, or other radiographicimaging. In one example, the variation in density can comprise a segmentor band of a high density material. In one example, the variation indensity can be a reduction in the thickness of the distal end of astructure. It is understood that the x-ray-visible markings can appearat other locations on the cannula 301, stylet 307, and electrode 342. Itis understood that the x-ray-visible markings can have similaradvantages to those of the echogenic markings described above.

In one example the electrode shaft, as illustrated in FIGS. 1 through 7,can be comprised of a rigid stainless steel tubing or other metaltubing. This has the advantage that the electrode shaft is robustagainst longitudinal or pushing force is which can be in encounteredduring insertion of the electrode through the cannula and on into bodilytissue beyond the end of the cannula.

Referring to FIG. 4, the components of embodiments of the presentinvention are shown in schematic in side elevation view. The electrodesystem can comprise multiple cannulas represented in FIG. 4 by theexamples of cannula 401, 409, and 417. These cannulas have differentshaft lengths designated by D1, D2, and D3, respectively. Each of theshafts of the cannulas is essentially fully insulated, as represented bythe hatched areas 404, 412, and 420, respectively. Each of the cannulashas a hub structure which is the same, represented by 406, 414, and 422,respectively. In one example, each of the cannulas can comprise a metalshaft with an insulated coating over. The metal shaft, in one example,can be a stainless steel hypodermic tubing, and the insulation can be ofvarious types of materials such as, for example, Teflon, polyurethane,or other common insulating plastics. In another example, the cannulashaft can comprise a plastic tubing into which the stylet and/or theelectrode can be passed. Another component in the system shown in FIG. 4is the rigid stylet system 430 which has a rigid shaft portion 431, ahub 440 with engagement element 437, and a sharpened tissue piercingdistal tip 434. As shown by the dashed lines with the arrows, the stylet430 can be inserted into any one of the multiple cannulas 401, 409, and417, so that when the stylet structure 440 engages with the respectivehubs 406, 414, or 422, the distal tip will extend beyond the distal endof the cannulas, such as and 407 on cannula 401, by the distances T1,T2, and T3, respectively. The lengths D1, D2, and D3 for each of thecannulas 401, 409, and 417, respectively, can have predetermined andknown values so that the respective tip extensions T1, T2, and T3 canalso be known and predetermined. Therefore, with a set of multiplecannulas with such known length with respect to the length of the styletsystem, the clinician can select an appropriate cannula so that thelength of the cannula accommodates an appropriate and desired range ofpenetration of the cannula when the cannula plus stylet system isinserted into the tissue and directed to and proximate to a targetvolume to be ablated, and the degree of stylet tip extension beyond thecannula distal end is appropriate for producing a tract within thetarget volume along which tract the high-frequency electrode cansubsequently follow preparatory to making a thermal ablation in thetarget volume. Also shown in FIG. 4 is a high-frequency electrode 450which has shaft 451, a hub 460 with engagement surface 457, and distalend 454. The electrode is adapted to be inserted into each of thecannulas 401, 409, or 417 so that when electrode hub 460 engages withthe respective hubs 406, 414, and 422, then the distal portion of theelectrode 450 will extend beyond the distal end of the cannulas by theamounts T1, T2, and T3, respectively. In one example of a sequence ofusage of these components, the composite of the stylet system insertedinto a selected stylet is initially inserted percutaneously into thebodily tissue towards a target volume. Then, when the stylet system isremoved from the cannula, and the high-frequency electrode is insertedinto the cannula, the length extension of the electrode beyond thecannula distal end can be essentially the same as the length ofextension of the stylet beyond the distal end of the cannula when thestylet system is engaged inside the cannula. The stylet system with istissue piercing tip will have made a tract in the target tissue, so thatwhen the electrode is subsequently inserted into the cannula after thestylet has been removed, and the electrode has an already establishedtract to follow through the target tissue along. This has one advantagethat the electrode, in one example, does not have to have a tissuepiercing distal tip since the stylet tract has already done the tissuepiercing and established a pathway along which the electrode distal endcan follow. The electrode system shown in FIG. 4, in one example, can bemade in different embodiments in which they cannulas shaft lengths D1,D2, and D3 and the length L of the stylet system 430 and/or theelectrode system 450 can have a selected and/or known and/orpredetermined lengths to accommodate different depths of penetrationtowards a target volume and different lengths of exposed tip extensionof the electrode beyond the cannula distal end to accommodate differentvolumes of thermal ablation to be made. For example, the overall lengthL of the stylet and/or electrode can be determined so that the hub totip distance D plus T, or in the case of a specific cannula D1 plus T1,can be a length of 10, 15, 20, 25, or 30 cm which provides a range ofdepth of penetration that can accommodate the skin to target depth formost target volumes within the body. For each of these lengths D plus T,a set of, for example, four cannula can be supplied each having theappropriate length so that T1 equals 4 cm, T2 equals 3 cm, T3 equals 2cm and T4 equals 1 cm. In this example, once the overall length D plus Thas been selected, the surgeon can now select from a set ofcorresponding cannulas the appropriate cannula so that the exposed tiplength of the ablation electrode can be selected as 1, 2, 3, or 4centimeters

Referring to FIG. 5, a schematic representation is shown of anarrangement of an electrode system, a high-frequency generator, and acoolant system that is adapted to be used to ablate a target volumewithin the living body. The living body is represented by the object B,the skin is represented by object S, and a target volume TV is shownwithin the living body which can be, for example, a tumor that is to bethermally ablated. An electrode system in accordance with the presentinvention is shown inserted percutaneously into the body. The electrodesystem comprises a cannula 301 that is, in one example, insulated over aportion of its surface, or in another example shown in FIG. 5, insulatedover its entire surface as indicated by the hatched area 304. In theexample shown in FIG. 5, the numbers correspond to the same numbersshown in the embodiment shown FIG. 3 above. In other examples, theconfigurations of FIG. 1, FIG. 2, and FIG. 4 could be substituted inthis schematic drawing of FIG. 5. In one example, the cannula length Dcan be selected so that the distal end of the cannula just reaches theouter perimeter of the target volume TV, as illustrated schematically inFIG. 5. In an initial insertion step not shown in FIG. 5, a rigid styletsuch a stylet 307 in FIG. 3 can be inserted into the cannula during thestep that the cannula is inserted percutaneously through the skin S andon into the target volume TV. The stylet can then be removed and theelectrode 342 can be inserted into the cannula 301, and the distaluninsulated portion of the electrode 342 extends beyond the distal endof the cannula by the distance T The length of the cannula D and therelative length of the electrode 342 can be preselected and known sothat the extension distance T accommodates the dimension of the targetvolume TV to be ablated. In an alternative embodiment of the systemshown in FIG. 5, multiple electrodes systems can be inserted into thetarget volume TV to produce an adequate length and lateral dimension ofthe ablation volume to cover the desired target volume TV, which, forexample, can be a cancerous tumor to be destroyed. Illustrations of useof multiple electrodes systems for ablation are shown in the referencescited in the BACKGROUND section above. Connected to the hub 348 of theelectrode 342 is a connection wire 360 that plugs into the output jack607 of high frequency generator 604, and this connects the output signalof the generator 604 which is active on the output Jack 607 to beconnected to the uninsulated extension portion 342 of the electrode.Another output Jack 611 on the generator 604 has a wire 614 thatconnects the output of the generator to a reference electrode 617 thatis attached to the patient's skin S. Therefore the signal output of thegenerator 604 that is generated across the output jacks 607 and 611 willcause high-frequency current to flow between the uninsulated electrodetip 342 and the surface area reference electrode 617. The high-frequencycurrent passing through the tissue of the body B, as described in thecited references in the BACKGROUND section above, this will causeheating of the tissue near and around the exposed electrode tip 342.Various forms of the reference electrode 617 are known, and they caninclude conductive metal plates, commercially available electricalgrounding pads used commonly in electrode surgery and high-frequencyapplications. In another example of a bipolar lesioning situation, asecond electrode can be placed into the target volume; then, each of theelectrodes can be connected to output jacks 607 and 611 so that thesignal output of the generator 604, such as RF voltage, is now impressedbetween the exposed tip so the two electrodes within the bodily tissue.Description of bipolar high-frequency heating of tissue between bipolarelectrodes is described in the references cited in the BACKGROUNDsection above. The high-frequency generator 604 can comprise a source ofhigh power high frequency output signal, controls and switching systemsthat regulate the level of output delivered to one or more electrodes asthe ablation process proceeds, and a graphics screen to display such asthe display 632 which can monitor electrical parameters associated withthe output signal and the electrodes such as RF current, power, voltage,and tissue impedance between the electrode and/or electrodes and thereference electrode 617. Examples of graphics displays, control systems,bipolar heating, and other control aspects of a high-frequency generatorare referred to in the cited references in the BACKGROUND section above.Also shown in FIG. 5 are fluid coupling connections 354 and 357 whichconnect to the electrode hub 348 on one end, and connect on the otherend to a cooled source 624. The cooled source 624 can comprise, in oneexample, a reservoir of cooled fluid such as chilled saline, a pumpsystem to pump the cooled fluid into the input tube 354, which passesthrough an internal cooling channel in the electrode 342, and exits bythe exit channel tube 357 to return to the coolant 624. Examples ofcooled systems are given in the cited references in the BACKGROUNDsection above. In one example, coolant fluid is pumped through theelectrode system as shown in FIG. 5, the same time that the outputsignal of the generator 604 is connected to the electrode tip 342. Thiscooled electrode system can produce larger ablation volumes thannon-cooled electrodes, and it is useful in the field of interventionalradiology for percutaneous minimal invasive ablative destruction ofcancerous tumors.

Referring to FIG. 6, a process is described according to the presentinvention for ablating a tissue volume near a target position in thebodily tissue, for example, a cancerous tumor or other diseased volumewithin an organ or within the tissue of the living body. In one example,the embodiment of a system and apparatus described herein in FIGS. 1through 5 and FIG. 7 can be used to implement the method described inFIG. 6. In step 601, the clinician can select the cannula and a styleteach having appropriate length so that when said stylet is inserted intosaid cannula so that the stylet hub engages the cannula hub, then thecombined system can have been appropriate length to approach a desiredtarget volume and provide sufficient extension of the stylet distal endbeyond the cannula distal end to span an appropriate length along thetarget volume. Throughout this description of the present invention, thestylet can comprise a variety of structures, including a rigid stainlesssteel rod with a pointed tip, or a needle structure which includes apointed tubular needle, which for example can be built from stainlesssteel tubing, together with an obturating needle stylet which wheninserted into the needle closes the open end of the needle and providesan adequate pointed tip to the composite needle structure. In oneexample, a set of cannulas can be provided with different cannula shaftlengths which the clinician can select from, and also a stylet with alength selectable by the clinician so that when the stylet is insertedinto a selected cannula, the distal end of the stylet will extend beyondthe distal end of the cannula by a known amount. In step 601, in oneexample, the clinician can choose a stylet of appropriate length at thebeginning of the process so that when the stylet is inserted into thecannula, and the composite cannula and stylet are inserted into thebodily tissue, then the composite length of the cannula and stylet willbe sufficient to reach the deepest portion of a selected target volume.In step 601, in one example, the clinician can choose the appropriatelength of the cannula, after having chosen a desired stylet length, sothat the distal end of the cannula will be near to the shallowestportion of the target volume and so that the portion of the stylet thatextends beyond the distal cannula tip adequately covers the length ofthe target volume along the direction in which the combined cannula andstylet is aimed into the target volume. In one example, step 601 cancomprise selecting an appropriate geometry of cannula and styletstructure as illustrated in the embodiments of FIGS. 1 through 7 herein.In one example related to step 601, a cannula and stylet system as shownin FIGS. 1A and 1B can be chosen so that the combined uninsulated distalend of the composite cannula and stylet, designated as U plus T in FIG.1A and FIG. 1B, corresponds to an appropriate the length of the ablationvolume along the cannula and stylet direction. In another examplerelated to step 601, a system is illustrated in FIG. 2 can be chosen bythe clinician so that the overall length of the cannula, E plus U, isappropriate for the anticipated depth of penetration beyond the skinsurface to the target position, and the exposed tip length U can bechosen to be appropriate for the length of the ablation volume to bemade within the target volume. In another example related to step 601,the system of FIG. 3 can be chosen in the composite shaft length, D plusT as designated in FIG. 3, is appropriate to achieve a desired positionof the stylet distal end within the target volume, and the cannulalength D can be chosen so that the distal end of the cannula 314 isapproximately at the tip of the nearest part of the target tissuevolume, and the exposed tip T corresponds to the approximate length ofthe target tissue volume to be ablated along the direction of theinsertion tract. In the example of FIG. 4 related to step 601, theclinician can choose from a multiplicity of cannulas such as 401, 409,and 417 to achieve the desired tip extension of the stylet, andtherefore the tip extension of the electrode, beyond the distal end ofthe cannula when the combine stylet and the cannula are inserted intothe tissue.

Referring to FIG. 6, in step 604 the combination of the stylet withinthe cannula, and in one example, with the engagement of their respectivehubs to each other as described in FIGS. 1 through 4 above, is insertedinto the bodily tissue so that the distal portion of the cannula and thedistal tip of the stylet are positioned in desired locations in or neara target volume in the tissue. In one example for illustration, using acannula and stylet system as shown in FIG. 3 and FIG. 4, step 604 cancomprise the step of positioning the distal end of the stylet atapproximately the deepest position of the ablation volume that isdesired within the target volume, and the distal portion of theinsulated portion of the cannula can be positioned approximately at theshallowest position relative the ablation volume that is desired. Inthat example, the extension portion of the stylet 307 beyond the cannuladistal end 314 can approximately span the length of the target volumealong the shaft direction. In another example, in which the cannulaand/or stylet has distance markings on it, as for example in theembodiment of FIG. 3, the clinician can observe which distance marker isat the surface of the patient's skin when the cannula plus stylet systemis inserted into the body, and by knowing the overall length D plus T,can calculate the depth relative to the skin of the distal end of thestylet within the bodily tissue. This depth can have been predeterminedby image and data prior to or during the time of surgery, as for exampleusing CT, MRI, or Ultrasound image data. Therefore, the markings on thecannula and/or cannula and stylet can be a visual indicator to theclinician of how deep the cannula and the distal tip of the stylet iswithin the body. The clinician commonly has done image and data of thepatient prior to surgery, and can therefore have predicted theappropriate depth below the skin of the limits of the target volume.Therefore this knowledge of the depth of the cannula and the extendedstylet tip can help guide the direction of the intervention. Similarillustrations can be made for the embodiments shown in the other figuresherein described.

Referring to FIG. 6, in step 607 the stylet can be removed from thecannula and the high-frequency electrode can be inserted into thecannula. In one example, the electrode can have an uninsulated distalportion a portion which, when the hub of the electrode and the hub ofthe cannula are engaged, extends beyond the distal end of the cannula bythe same distance that the distal end of the stylet extends beyond thedistal into the cannula when the stylet is inserted into the cannula. Inone example therefore, the depth measurements and positioning which wereestablished by the clinician in step 601 and 604, correspond toequivalent depth measurements in positions of the extended electrode tipas for when previously the stylet was inserted into the cannula. In oneexample, the electrode can be a non-cooled electrode, for example, nothaving an internal coolant passing within it to cool the distal exposedextended tip of the electrode and cannula. In another example, theelectrode can have an internal cooling channel and input and outputports near its hub to enable flow of a coolant fluid through theelectrode, as described previously herein and in the references, so asto cool the distal uninsulated portion of the electrode that extendsbeyond the distal end of the cannula. In another example such asillustrated by the embodiments of FIGS. 1A, 1B, and 2, the cooling ofthe electrode can result in cooling of the distal exposed portion of thecannula through which the electrode passes. This can enable cooling ofthe uninsulated portion of the cannula that contributes to theenergizing of surrounding tissue with the output signal of ahigh-frequency generator so as to heat the surrounding tissue.

Referring to FIG. 6, step 612 comprises connecting the electrode to ahigh-frequency generator so that output signal of the generator isconnected to the electrode. In one example the electrode shaft can becompletely uninsulated, so that it makes electrical contact with thecannula, and also so that the distal portion of the electrode thatextends beyond the distal end of the cannula is uninsulated and makeselectrical contact with surrounding tissue for the purpose of heatingthe tissue. In one example, the cannula can comprise a metal conductivetubing which has an uninsulated portion on this distal end, andtherefore connecting the electrode to the output signal can also connectthe output signal to the exposed portion of the cannula, which in turnmakes electrical contact with the surrounding tissue to heat the tissue.Step 612 can also comprise, in the example where the electrode has aninternal cooling channel with input and output ports connected to thechannel for flowing a cooling fluid through the electrode, connectingthe input and output ports on the electrode to a source of coolantfluid, so that when the cooling fluid flowing, the distal portion of theelectrode that extends beyond the cannula distal end is cooled, and inthe case that the cannula has an exposed portion, then exposed cannulaportion can also be cooled.

Referring to FIG. 6, step 616 comprises applying the output signal fromthe generator to the electrode to cause a high-frequency current to flowthrough the electrode to the tissue that surrounds the uninsulatedportion of the electrode that extends beyond the distal end of thecannula, and in the case that the cannula has an uninsulated portion,high-frequency current will also flow through the electrode to thecannula, and consequently to the tissue surrounding the uninsulatedportion of the cannula. In the case that the electrode is adapted forfluid cooling, the uninsulated portion of the electrode, and theuninsulated portion of the cannula, is cooled when the output signal ofthe generator is connected to the electrode. The cooling of theelectrode and cannula exposed portions can alter the heatingdistribution of the tissue around the electrode and cannula, in oneexample can increase the size of the ablation volume of the tissuesurrounding the electrode and cannula tips. In one example, feedbackcontrol of the output signal can be used to regulate the heating of thebodily tissue. In one example, manual control of the output signal canbe used to regulate the heating of the bodily tissue. In one example, atemperature measured at or near the electrode tip can be used toregulate the output signal. In one example, an impedance of the measuredbetween two output jacks of an high frequency generator can be used toregulate the output signal. In one example, electrical outputmeasurements, such as Voltage, Current, Power, can be used to regulatethe output signal.

Referring to FIG. 7, a side elevation view in partial sectional view isshown of one embodiment of the present invention showing aspects of theinternal cooling system and electrical and thermal connections.Electrode shaft 701 can comprise, in one example, a rigid stainlesssteel tubing. In one example, a rigid stainless steel tube is mainstructural element of the electrode shaft 701, providing stiffness andrigidity to the electrode shaft 701. In one example, the electrodedistal shaft can have a distal tip 707 that has a non-tissue piercingshape such as a rounded or elliptically shaped contour. In anotherexample, distal tip 707 can be a tissue piercing point having asharpened tip such as a trocar or a beveled needlelike tip. In anotherexample, the electrode shaft 701 can comprise a catheter type structurewhich has a portion of its external surface that is electricallyconductive. In one example, the electrode shaft can comprise a cathetermade of a plastic material that can have on its external surface ametalized coating or a conductive wire helix or mesh outside layer sothat its external surface is a substantially exposed electricallyconductive surface. At the proximal end of a metal shaft 701, in oneexample the shaft is connected to a hub 704 at the junction 709. Thejunction 709 can be, for example, a glued joint that can be mechanicallyrobust and also be sealed to fluid pressure to prevent leaks of acoolant fluid within the electrode. In one example, the hub 704 can beconstructive of a plastic insulating material. In another example, thehub 704 can be made of a metal or other rigid material. In one example,and electrical conductor 711 connects the output signal from thehigh-frequency generator by the electrical junction 716 to theconductive portion of the electrode shaft 701. In one example, theconductor 711 can be an electrical wire. Also shown is electricalconnection 714 which can carry temperature sensing information from atemperature sensor 724 inside the shaft 701 of the electrode. In oneexample, element 714 can comprise thermocouple wires, for example copperand constantan wires, which connect electrically at 724 to form athermocouple junction at position 724. In another example, 714 cancomprise a stainless steel tubing inside of which are thermocouple wireelements that connect to a thermocouple junction 724. In one example,714 can be a thin stainless steel tubing inside of which is a constantanwire that is electrically connected to the stainless steel tubing near724 to provide a stainless steel to constantan thermocouple junctionwhich provides temperature sensing information at the distal location724. In another example, 714 can be a stainless steel tubing inside ofwhich is a constantan wire and a copper wire which are electricallyconnected at the distal portion of the tubing 724 to provide temperaturesensing information at the position 724. In one example, thehigh-frequency or RF carrying wire elements represented by 711 can bepart of the element 714. The electrical connection of the output signalfrom the high-frequency or RF generator can be made to a thin stainlesssteel tubing that is part of 714, and the electrical connection of theoutput signal to the exterior stainless steel conductive tubing 701 canbe made by means of contact of element 714 to the inside of thestainless steel tubing 701. In that example, the electrical connectionof 711 to the conductive tubing 701 by the junction 716 can beeliminated. In one example, multiple temperature-sensing elements, like724, can be incorporated into the electrode at multiple locations. Inone example, the output signal carrying elements and the temperaturesensing elements, exemplary embodiments of which have been describedherein in the references, can be carried back out of the hub by conduit747. In one example, conduit 747 can be flexible plastic tubing and canbe connected to the output jacks of a high-frequency generator by meansof connection junctions and/or extension cables, which are not shownexplicitly in FIG. 7 and examples of which are shown in the embodimentsin the references cited in the BACKGROUND section herein. The outputgenerator can be adapted to measure of the temperature signal at thetemperature sensor 724 as well as to supply signal output to theelectrode out of shaft 701. Also shown in FIG. 7, a fluid flow path andinput and output connections can provide coolant flow within theelectrode 701 in order to cool the electrode during application of RF orhigh frequency output signal from an RF generator. An inflow tubing line732 carries coolant fluid into the electrode, illustrated by arrow 737.In one example, input tubing 732 connects to an internal inflow tubing721, which is contained within the electrodes 701 and runs along theinterior of the of the electrode shaft 701, and which carries coolantfluid to the distal end of the electrode. The distal end 722 of thetubing 721 can be an opening in the tubing which enables coolant fluidthat is pumped in through 732 to exit into the inner space of theelectrode shaft tubing 701 near the distal end 707 as illustrated by thearrow 727 and 728. The fluid exits the tubing 722 circulates back asillustrated by arrows 727 and 728 and flows backwards through theinterior lumen 720 of tubing 701, and then flows into the exit tube 742to exit the hub as illustrated by arrow 744. In one example, theexternal connection 732 can be a plastic tubing, and the inner inflowtubing 721 can be a metal tubing such as a stainless steel hypodermictubing. The proximal end of the hub 714 can be fluid sealed by a sealantillustrated by the hatched area 754. In one example, sealant 754 cancomprise an epoxy seal in which, and in one example, the epoxy can beinjected around the tubing's 732, 742, and 747 as well as the proximalend of the hub 704 itself so that any fluid under pressure in the innerspace 768 of hub 714 will be sealed against any escape path out of theproximal end of the hub. In one example, the hub 704 and it's distal endis fluid sealed to the electrode shaft 701 at the junction 709 so thatcoolant fluid under pressure within the inner space 720 of the electrodeshaft tubing and the inner space 768 of the hub 704, will be sealedagainst fluid leaks.

Referring to FIG. 7, this embodiment has one advantage that thegeometric arrangement of the tubing 732, 742, and 747 that connect tothe hub 704 and to the internal shafts within the electrode shaft 701can be made in a very compact and efficient form. In one example, theinput tubing's 732, 742, and 747 can have outer diameters in the rangeof 1 to 2 mm. These can be joined to a hub 704 that has an outerdiameter HD which, in one example, can be between 9 and 15 mm. In oneexample, the hub diameter can be approximately 10 mm. In anotherexample, the hub diameter and be less 5 millimeters In another example,the hub diameter can be 3 mm. In another example, the hub diameter canbe 4 mm. In another example, the hub diameter can be 5 mm. In anotherexample, the hub diameter can be 6 mm. In another example, the hubdiameter can be 7 mm. In another example, the hub diameter can be 8 mm.In another example, the hub diameter can be 9 mm. This small diameterelectrode has one advantage that multiple such mechanically independentelectrodes can be inserted into the body towards a target volume withthe electrode shaft and hubs clustered close together. In one example, aset of multiple electrodes, as exemplified in the embodiments of FIGS. 1through 7, can be inserted into the patient's body in a parallelclustered configuration with the electrode separation of approximately10 mm. This has the advantage that using mechanically independentelectrodes, a clustered set of cooled RF electrodes can be arranged inan internal target volume. In one example, as an illustration of thisadvantage, a tight cluster of several such electrodes can be insertedbetween the ribs to approach a target volume in the liver or in thelung. The small diameter of the hub can has one advantage that themultiple electrodes can be clustered in a close together arrangement toapproach a deep target through the limited space between the patient'sribs. Because the compact construction of the hub, as exemplified byFIG. 7, in one example, a hub diameter HD of approximately 10 mm isachieved which is substantially smaller than previously implementedcooled RF electrodes as exemplified by the electrodes of Valley lab,Radionics, and Baylis referred to in the BACKGROUND section above.Another advantage of the configuration in FIG. 7 is that the length HLof the hub 704 can be made significantly shorter and lighter weight thanthe hubs of previous cooled RF electrode systems of Valley lab,Radionics, and Baylis, referred to in the BACKGROUND section. In oneexample, the length HL can be in the range of 0.5 to 1.5 inches. Oneadvantage of smaller diameter HD and the shorter length HL of the designof FIG. 7, is that the hub can be light weight and unobtrusive. This hasthe advantage that there can be less torque applied to the shaft of 701when the electrode is inserted into the patient's body, which reducesthe chance of the electrode moving from its desired target position onceelectrode has been established in that target position.

Referring to FIG. 7, in another aspect, the arrangement of elements inthis embodiment of the invention within the electrode shaft 701 enablesa compact, simplified, and easily manufactured electrode. In one exampleelectrode shaft 701 can have a rigid stainless steel tubing constructionwith the other diameter SD of the electrode shaft being in the range of1 to 2 mm. In one example, the element 714 can comprise a thin metalstainless steel tubing having outer diameter between 0.1 and 0.5 mm, andcan carry the RF signal by being connected electrically through cable747 to the output of the RF generator. Inside of tubular element 714 canbe a thermocouple element such as a constantan wire that enables thethermocouple junction to be positioned at the distal end 724. Theinternal inflow tubular element 721 can be a thin-walled stainless steeltubing with diameter in the range of 0.1 to 0.7 mm. One advantage isthat the use of a single internal inflow tubing 721, with return fluidflow passing through the inner space 720 of the electrode shaft 701enabling the fluid to pass into the hub chamber 768 and out the exit to742, there is a very efficient low impedance fluid passageway of thecoolant fluid unit out of the electrode shaft while maintaining a smalldiameter of the electrode shaft. In one example, the length of the shaftSL can range from 5 cm to 30 cm, or more. Electrodes of different shaftlengths can be made available so that the clinician can select thedesired length on the application and on the depth of the target tissuewithin the body to be reached.

Referring to FIG. 7, in another example, the tube 744 can carry inflowof cooling fluid, and the tube 737 can carry outflow of cooling fluid.

In FIGS. 1 through 7, the shaft of the electrode can have a mainstructural element which provides rigidity and stiffness to theelectrode shaft comprising a metal tubing that is part of the outer wallof the electrode shaft.

A number of embodiments of the invention have been described.Nevertheless, it will be understood that various modifications may bemade without departing from the spirit and scope of the invention.Accordingly, other embodiments are within the scope of the followingclaims.

The invention claimed is:
 1. An electrode system adapted forintroduction into bodily tissue comprising: at least two cannulas, eachof the cannulas having a cannula distal end and a cannula proximal end,each of the cannulas having a cannula hub fixedly attached at thecannula proximal end without a set screw or a user-adjustable device,each of the cannulas having a cannula shaft having a lumen therethrough,and the cannula shaft having a cannula insulated portion of its externalsurface that is insulated; a stylet having a stylet shaft with a styletdistal end and a stylet proximal end, the stylet having a stylet hubfixedly attached at the stylet proximal end without a set screw or auser-adjustable device; and an electrode having an electrode shaft withan electrode distal end and an electrode proximal end, the electrodehaving an electrode hub fixedly attached at the electrode proximal endwithout a set screw or a user-adjustable device, the electrode shafthaving at least in part an electrode uninsulated portion on its surface,whereby when the stylet shaft is inserted into the cannula lumen of oneof the at least two cannulas, said stylet hub engages with the cannulahub of the one of the at least two cannulas such that the stylet has apredetermined stylet length between the distal end of the stylet shaftand the point of engagement between the stylet hub and the cannula huband the combination of the one of the at least two cannulas and saidstylet is adapted to be inserted into the bodily tissue, and when theelectrode shaft is inserted into the cannula lumen of the one of the atleast two cannulas with the stylet not inserted in the cannula lumen,said electrode hub engages with the cannula hub of the one of the atleast two cannulas such that the electrode has a predetermined electrodelength between the distal end of the electrode shaft and the point ofengagement between the electrode hub and the cannula hub, at least apart of the electrode uninsulated portion is within said lumen of theone of the at least two cannulas, and the combination of the cannulashaft of one of the at least two cannulas and the electrode shaft form acombined exposed tip having an uninsulated external surface of saidcombination of shafts, wherein the predetermined electrode length issubstantially the same as the predetermined stylet length such that saidelectrode distal end is in substantially the same position relative tothe cannula distal end of the one of the at least two cannulas as issaid stylet distal end is relative to the cannula distal end of the oneof the at least two cannulas; wherein said electrode is adapted forconnection to a high-frequency generator so that output signal from thehigh-frequency generator is connected to said electrode uninsulatedportion, and when said electrode is inserted into any of the at leasttwo cannula, said combined exposed tip is configured to deliver outputsignal from the high-frequency generator; wherein said electrode has aninternal fluid channel, a fluid input port and a fluid output port, theinput port being adapted to be connected to a source of coolant fluid sothat the coolant fluid can flow into the fluid input port, through theinternal fluid channel, and out of the fluid output port, whereby saidcombined exposed tip is cooled by said coolant fluid when said electrodeis inserted into any of the at least two cannulas; and wherein when theelectrode shaft is inserted into any of the at least two cannulas, eachof the combination of electrode shaft and one of the at least twocannulas form a combined exposed tip of a different length.
 2. Thesystem of claim 1, wherein the length of said stylet shaft and saidelectrode shaft are substantially equal.
 3. The system of claim 1,wherein said stylet shaft is a rigid tissue piercing shaft.
 4. Thesystem of claim 1, wherein said electrode shaft has a non-tissuepiercing tip at said electrode distal end.
 5. The system of claim 1,wherein said electrode shaft has a tissue piercing tip at said electrodedistal end.
 6. The system of claim 1, and further including a conductivewire adapted to connect said electrode to the output signal of thehigh-frequency generator.
 7. The system of claim 1, wherein said styletcomprises a hollow needle with an obturating stylet that is adapted tobe inserted into the needle.
 8. The system of claim 1, wherein the hubof said electrode is 10 mm or less in width.
 9. The system of claim 1,wherein substantially all of the external structural element of saidelectrode shaft comprises a rigid metal tube.
 10. The system of claim 1,wherein each of said at least two cannulas, and/or stylet, and/orelectrode comprises x-ray visible markings at known positions on theirshafts so that when the combination of one of the at least two cannulasand said stylet, or the combination of one of the at least two cannulasand said electrode are inserted into the patient's body tissue, anx-ray, fluoroscopy, CT, or other radiographic imaging machine can beused to visualize the position of portions of the cannula, and/or saidstylet, and/or said electrode relative to the structures in thepatient's body.
 11. The system of claim 1, wherein each of said at leasttwo cannulas, and/or stylet, and/or electrode comprises ecogenicmarkings at known positions on their shafts so that when the combinationof one of the at least two cannulas and said stylet, or the combinationof one of the at least two cannulas and said electrode are inserted intothe patient's body tissue, an ultrasonic imaging machine can be used tovisualize the position of portions of the cannula, and/or said stylet,and/or said electrode relative to the structures in the patient's body.12. The system of claim 1, wherein said stylet comprises a needle and aneedle's stylet which have a sharpened tissue piercing point.
 13. Thesystem of claim 1, wherein said known length is greater than 6 mm. 14.The system of claim 1, wherein said predetermined electrode length isabout 10 mm.
 15. The system of claim 1, wherein said predeterminedelectrode length is about 20 mm.
 16. The system of claim 1, wherein saidpredetermined electrode length is about 30 mm.
 17. The system of claim1, wherein said predetermined electrode length is about 40 mm.
 18. Thesystem of claim 1, wherein said predetermined electrode length is about25 mm.
 19. The system of claim 1, wherein said predetermined electrodelength is about 50 mm.
 20. The system of claim 1, wherein saidpredetermined electrode length is about 60 mm.
 21. The system of claim1, wherein said predetermined electrode length is greater than 60 mm.22. The system of claim 1, wherein the surface of the electrode shaft ismetal.
 23. The electrode system of claim 1 wherein, each of said cannulashafts has the cannula insulated portion and a cannula uninsulatedportion, the cannula uninsulated portion comprises an uninsulatedsurface of the cannula shaft at the cannula distal end of known cannulatip length, wherein each of the at least two cannulas uninsulatedportion forms a part of the combined exposed tip, and said electrode andeach cannula are adapted so that said electrode distal end cools thecannula uninsulated portion when said electrode is inserted into one ofthe at least two cannulas.
 24. The system of claim 23, wherein saidcombination of said stylet and one of the at least two cannulas has acombined distal tip having a sharpened tissue piercing point.
 25. Thesystem of claim 23, wherein said known cannula tip length is about 10mm.
 26. The system of claim 23, wherein said known cannula tip length isabout 20 mm.
 27. The system of claim 23, wherein said known cannula tiplength is about 30 mm.
 28. The system of claim 23, wherein said knowncannula tip length is about 40 mm.
 29. The system of claim 23, whereinsaid known cannula tip length is about 25 mm.
 30. The system of claim23, wherein said known cannula tip length is about 50 mm.
 31. The systemof claim 23, wherein said known cannula tip length is about 60 mm. 32.The system of claim 23, wherein said known cannula tip length is greaterthan 60 mm.
 33. The system of claim 23, wherein said predeterminedelectrode length and predetermined stylet length are a known length foreach of said at least cannulas.
 34. An electrode system adaptedintroduction into bodily tissue comprising: at least two cannulas, eachcannula having a cannula distal end and a cannula proximal end, thecannula having a cannula hub fixedly attached at the cannula proximalend, the cannula having a cannula shaft at the distal end, the cannulahaving a lumen therethrough, the cannula shaft being substantiallyinsulated, the cannula having a predetermined cannula length; whereinthe cannula lengths of the at least two cannulas are different from eachother; a tissue piercing needle having a needle shaft with a needledistal end and a needle proximal end, said needle having a shaft portionthat is adapted to be inserted into the cannula lumen of any of the atleast two cannulas the tissue piercing needle having a needle hubfixedly attached at a proximal end of the tissue piercing needle andhaving a sharpened tissue piercing point on a distal end of the tissuepiercing needle, the needle having a predetermined electrode lengthbetween the distal end of the needle shaft and the part of the needlehub that is configured to engage with the cannula hub of any of the atleast two cannulas; an electrode having an electrode shaft with anelectrode distal end and an electrode proximal end, said electrodehaving a shaft portion that is adapted to be inserted into the cannulalumen of any of the at least two cannulas, the electrode having anelectrode hub fixedly attached at the electrode proximal end, theelectrode having a predetermined electrode length between the distal endof the electrode shaft and the part of the electrode hub that isconfigured to engage with the cannula hub of any of the at least twocannulas; wherein the electrode length and the needle length beingsubstantially equal: wherein the electrode hub and the cannula hub ofany of the at least two cannulas are configured to engage with eachother without a set screw or a user-adjustable device; whereby when theneedle shaft of said tissue piercing needle is inserted into the cannulalumen of one of the at least two cannulas such that said tissue piercingneedle hub engages with the cannula hub of the one of the at least twocannulas without a set screw or a user adjustable device, the distal endof the tissue piercing needle extends beyond the cannula distal end ofthe one of the at least two cannulas by a predetermined and known lengthand the one of the at least two cannulas and said tissue piercing needleare adapted to be inserted together into the bodily tissue so that thedistal end of the tissue piercing needle is located at a target positionwithin said bodily tissue, and whereby when the tissue piercing needleis removed from the cannula lumen of the one of the at least twocannulas and said electrode is inserted into the one of the cannula ofthe at least two cannulas, said electrode hub engages with the cannulahub of one of the at least two cannulas, the portion of the electrodeshaft that extends beyond the cannula distal end is uninsulated, and theelectrode distal end extends beyond the cannula distal end by the samelength as said predetermined and known length of the tissue piercingneedle so that said distal end of the electrode is directed along a sametract as said tissue piercing needle within the one of the at least twocannulas and is adapted to be located at the same target position withinsaid bodily tissue; wherein said electrode is adapted to be connected toa high-frequency generator so that said uninsulated portion of theelectrode shaft that extends beyond the cannula distal end of any of theat least two cannulas is configured to output signal from thehigh-frequency generator; wherein said electrode has an internal fluidchannel, a fluid input port and a fluid output port the input port beingadapted be connected a source of coolant fluid so that the coolant fluidcan flow into the input port, through the internal fluid channel, andout of the output port, whereby said uninsulated portion of saidelectrode that extends beyond the cannula distal end any of the at leasttwo cannulas is cooled by said coolant fluid; and wherein each of the atleast two cannulas provides for a different length of said uninsulatedportion of the electrode shaft that extends beyond the cannula distalend when the electrode shaft is inserted into each of the at least twocannulas.
 35. The system of claim 34, wherein the length of said needleshaft and said electrode shaft are substantially equal.
 36. The systemof claim 34, wherein said needle shaft is a rigid tissue piercing shaft.37. The system of claim 34, wherein said electrode shaft has anon-tissue piercing tip at said electrode distal end.
 38. The system ofclaim 34, wherein said electrode shaft has a tissue piercing tip at saidelectrode distal end.
 39. The system of claim 34, and further includinga conductive wire adapted to connect said high-frequency electrode tothe output signal of a high-frequency generator.
 40. The system of claim34, wherein said known length is greater than 6 mm.
 41. The system ofclaim 34, wherein said predetermined and known length is about 10 mm.42. The system of claim 34, wherein said predetermined and known lengthis about 20 mm.
 43. The system of claim 34, wherein said predeterminedand known length is about 30 mm.
 44. The system of claim 34, whereinsaid predetermined and known length is about 40 mm.
 45. The system ofclaim 34, wherein said predetermined and known length is about 50 mm.46. The system of claim 34, wherein said predetermined and known lengthis about 60 mm.
 47. The system of claim 34, wherein said predeterminedand known length is greater than 60 mm.
 48. The system of claim 34,wherein each of said at least two cannulas, and/or tissue-piercingneedle and/or electrode comprises ecogenic markings at known positionson their shafts so that when the combination of one of the at least twocannulas and said tissue-piercing needle, or the combination of one ofthe at least two cannulas and said electrode are inserted into thepatient's body tissue, an ultrasonic imaging machine can be used tovisualize the position of portions of the cannula, and/or saidtissue-piercing needle, and/or said electrode relative to the structuresin the patient's body.
 49. The system of claim 34, wherein each of saidat least two cannulas, and/or tissue-piercing needle, and/or electrodecomprises x-ray visible markings at known positions on their shafts sothat when the combination of one of the at least two cannulas and saidtissue-piercing needle, or the combination of one of the at least twocannulas and said electrode are inserted into the patient's body tissue,an x-ray, fluoroscopy, CT, or other radiographic imaging machine can beused to visualize the position of portions of the cannula, and/or saidtissue-piercing needle, and/or said electrode relative to the structuresin the patient's body.
 50. The system of claim 34, wherein the diameterof said electrode hub is less than 10 mm.
 51. The system of claim 34,wherein said length of extension is a known length for each of said atleast two cannulas.
 52. The system of claim 34, wherein substantiallyall of the outer portion of said electrode shaft comprises a rigid metaltubing.
 53. The system of claim 34, wherein substantially all of saidelectrode shaft has an uninsulated conductive surface.
 54. A system forheating of bodily tissue comprising: at least two cannulas of differentlengths, each cannula having a cannula distal end and a cannula proximalend, the cannula having a cannula hub fixedly attached at the cannulaproximal end, said cannula having a cannula shaft having a lumentherethrough, and the cannula shaft being substantially insulated; atissue piercing needle having a needle shaft with a needle distal endand a needle proximal end, the needle having a needle hub fixedlyattached at the needle proximal end and having a sharpened tissuepiercing point on the needle distal end, the needle shaft having apredetermined needle length from the distal end of the needle hub to thedistal end of the needle shaft, the tissue piercing needle configured tobe inserted into the cannula lumen of any of the at least two cannulas,and the needle hub and the cannula hub being configured to engage witheach other without a set screw or a user-adjustable device, so that whenthe tissue piercing needle is inserted into the cannula lumen of one ofthe at least two cannulas and said needle hub engages with the cannulahub of one of the at least two cannulas, the needle distal end extendsbeyond the cannula distal end by a known predetermined extension lengthof the one of the at least two cannulas, and said tissue piercing needleand the one of the at least two cannulas are inserted together intobodily tissue so that said distal end of said tissue piercing needle isadapted to be located at a target position in the bodily tissue; ahigh-frequency electrode having an electrode shaft with an electrodedistal end and an electrode proximal end, the high-frequency electrodehaving an electrode hub fixedly attached at a proximal end of thehigh-frequency electrode, the electrode shaft having a predeterminedelectrode length from the distal end of the electrode hub to the distalend of the electrode shaft, the electrode length being substantiallyequal to the predetermined needle length, the electrode shaft configuredto be inserted into the cannula lumen of any of the at least twocannulas, and the electrode hub and the cannula hub being configured toengage with each other without a set screw or a user-adjustable device,so that when said electrode hub engages with the cannula hub of the oneof the at least two cannulas, the portion of the electrode shaft thatextends beyond the cannula distal end is uninsulated, and theuninsulated extension portion of the electrode shaft extends beyond thecannula distal end by the same known predetermined extension length forthat cannula and is adapted to be located at the target position in thebodily tissue, wherein the distal end of said high-frequency electrodeis directed along the tract that is the same as the tract of the tissuepiercing needle when its hub was engaged with the cannula hub; whereinsaid electrode further comprises an internal fluid channel, a fluidinput port and a fluid output port; the input and output ports beingadapted to be connected to a source of coolant fluid so that the coolantfluid can flow into the input port, through the internal fluid channel,and out of the output port, whereby said uninsulated portion of saidelectrode that extends beyond the cannula distal end is cooled by saidcoolant fluid; a high-frequency generator adapted to produce an outputsignal, and for connection of the high-frequency generator to saidhigh-frequency electrode, and said high-frequency electrode beingadapted so that when connected to said high-frequency generator, saiduninsulated extension portion of said high-frequency electrode isconnected to said output signal and said output signal is adapted tocause heating of the bodily tissue near said uninsulated extensionportion of said high-frequency electrode; and wherein the knownpredetermined extension length of the uninsulated extension portion ofthe electrode shaft is different for each of the at least two cannulas.55. The system of claim 54, wherein substantially all of the length ofsaid electrode shaft has a conductive uninsulated surface.
 56. Thesystem of claim 54, wherein each of the at least two cannulas, and/ortissue piercing needle, and/or electrode comprises ecogenic markings atknown positions on their shafts so that when the combination of one ofthe at least two cannulas and said tissue piercing needle, or thecombination of one of the at least two cannulas and said electrode areinserted into the patient's body tissue, an ultrasonic imaging machinecan be used to visualize the position of portions of the cannula, and/orsaid tissue piercing needle, and/or said electrode relative to thestructures in the patient's body.
 57. The system of claim 54, whereineach of the at least two cannulas, and/or tissue piercing needle, and/orelectrode comprises x-ray visible markings at known positions on theirshafts so that when the combination of one of the at least two cannulasand said tissue piercing needle, or the combination of one of the atleast two cannulas and said electrode are inserted into the patient'sbody tissue, an x-ray, fluoroscopy, CT, or other radiographic imagingmachine can be used to visualize the position of portions of thecannula, and/or said tissue piercing needle, and/or said electroderelative to the structures in the patient's body.
 58. An electrodesystem adapted for introduction into bodily tissue comprising: at leasttwo cannulas of different lengths, each cannula having an internal lumenand having a cannula shaft portion to be inserted into the living body,the shaft portion being substantially insulated, and a cannula shaftportion having a cannula distal end and a cannula proximal end, thecannula distal end having an opening that connects to the internallumen, and the cannula proximal end being immovably connected to acannula hub; an insertion needle that is adapted to be inserted into theinternal lumen of any of the at least two cannulas, the insertion needlehaving a needle shaft portion that has a needle distal end and a needleproximal end, a distal end of the insertion needle being adapted topierce the tissue of the living body, and a proximal end of theinsertion needle being immovably connected to a needle hub, and theneedle shaft portion having a predetermined needle length so that whenthe needle shaft portion is inserted into a cannula internal lumen ofone of the at least two cannulas so that the cannula hub and said needlehub are in a predetermined needle hub position relative to the cannulahub, the assembly of said insertion needle within the cannula is adaptedto be inserted into the tissue of the living body, and said distal endof the insertion needle will extend beyond the cannula distal end by apredetermined extension distance greater 6 mm; wherein the predeterminedextension distance is different for the at least two cannula; ahigh-frequency electrode that is adapted to be inserted into saidinternal lumen of any of the at least two cannulas, the high-frequencyelectrode having an electrode shaft portion that has an electrode distalend and an electrode proximal end, the electrode proximal end beingimmovably connected to an electrode hub, and the electrode shaft portionis substantially uninsulated, and the electrode shaft portion having apredetermined electrode length that is substantially equal to the needlelength, so that when the electrode shaft portion is inserted into thecannula internal lumen of one of the at least two cannulas so that thecannula hub and said electrode hub are in a predetermined electrode hubposition relative to the cannula hub, an uninsulated portion of saidelectrode shaft electrode extends beyond the cannula distal end and saidelectrode distal end extends beyond the cannula distal end by saidpredetermined extension distance, the distal end of said electrodedirected along a tract that is the same as the tract as said insertionneedle within said cannula so that said electrode distal end is locatedat the same target position; wherein the needle hub position is notpredetermined by a set screw or a user-adjustable device, and the saidelectrode hub position is not predetermined by a set screw or auser-adjustable device; and wherein said electrode comprises an internalfluid channel, a fluid input port and a fluid output port; the inputport being adapted to be connected to a source of coolant fluid so thatthe coolant fluid can flow into the input port, through the internalfluid channel, and out of the output port, whereby the electrode shaftportion is cooled by said coolant fluid.
 59. The system of claim 58,wherein each of said at least two cannulas, and/or insertion needle,and/or high-frequency electrode comprises ecogenic markings at knownpositions on their shafts so that when the combination of one of said atleast two cannulas and said insertion needle, or the combination of oneof said at least two cannulas and said high-frequency electrode areinserted into the patient's body tissue, an ultrasonic imaging machinecan be used to visualize the position of portions of the one of the atleast two cannulas, and/or said insertion needle, and/or saidhigh-frequency electrode relative to the structures in the patient'sbody.
 60. The system of claim 58, wherein each of said at least twocannulas, and/or insertion needle, and/or high-frequency electrodecomprises x-ray visible markings at known positions on their shafts sothat when the combination of one of at least two cannulas and saidinsertion needle, or the combination of one of at least two cannulas andsaid high-frequency electrode are inserted into the patient's bodytissue, an x-ray, fluoroscopy, CT, or other radiographic imaging can beused to visualize the position of portions of the at least two cannula,and/or said insertion needle, and/or said high-frequency electroderelative to the structures in the patient's body.
 61. The electrodesystem of claim 23, wherein the cannula uninsulated portion of each ofthe at least two cannulas is substantially all of said combined exposedtip.